Revert "Add parents field to logEntry soy data for use in custom templates"

This reverts commit f1112ac7b9f4ffd31fc35a9832b15b5fcac4faca. It
throws an exception on the repository index page due to lacking the
revision information needed to render the diff field in a RevCommit:

```
com.google.gitiles.GitilesView$InvalidViewException: missing revision on DIFF view
  at com.google.gitiles.GitilesView$Builder.checkView(GitilesView.java:379)
  at com.google.gitiles.GitilesView$Builder.checkRevision(GitilesView.java:402)
  at com.google.gitiles.GitilesView$Builder.checkPath(GitilesView.java:416)
  at com.google.gitiles.GitilesView$Builder.checkDiff(GitilesView.java:407)
  at com.google.gitiles.GitilesView$Builder.build(GitilesView.java:344)
  at com.google.gitiles.GitilesView$Builder.toUrl(GitilesView.java:374)
  at com.google.gitiles.CommitSoyData.toSoyData(CommitSoyData.java:195)
  at com.google.gitiles.CommitSoyData.toSoyData(CommitSoyData.java:120)
  at com.google.gitiles.LogSoyData.toEntrySoyData(LogSoyData.java:138)
  at com.google.gitiles.LogSoyData.renderStreaming(LogSoyData.java:105)
  at com.google.gitiles.RepositoryIndexServlet.doGetHtml(RepositoryIndexServlet.java:136)
```

Bug: Google b/296133417
Change-Id: I26f68e05755ac28d6688b1ba8610e16bceaecec5
diff --git a/java/com/google/gitiles/LogSoyData.java b/java/com/google/gitiles/LogSoyData.java
index 9cffbb3..34b290f 100644
--- a/java/com/google/gitiles/LogSoyData.java
+++ b/java/com/google/gitiles/LogSoyData.java
@@ -47,8 +47,7 @@
           Field.AUTHOR,
           Field.COMMITTER,
           Field.BRANCHES,
-          Field.TAGS,
-          Field.PARENTS);
+          Field.TAGS);
   private static final ImmutableSet<Field> VERBOSE_FIELDS = Field.setOf(FIELDS, Field.DIFF_TREE);
 
   /** Behavior for the footer link when rendering streaming log data. */
diff --git a/resources/com/google/gitiles/templates/LogDetail.soy b/resources/com/google/gitiles/templates/LogDetail.soy
index 095edbb..23ae8eb 100644
--- a/resources/com/google/gitiles/templates/LogDetail.soy
+++ b/resources/com/google/gitiles/templates/LogDetail.soy
@@ -108,7 +108,6 @@
   {@param author: ?}  /** author information with at least "name" and "relativeTime" keys. */
   {@param committer: ?}  /** committer information with at least "time" and "relativeTime" keys. */
   {@param branches: ?}  /** list of branches for this entry, with "name" and "url" keys. */
-  {@param parents: ?}  /** unused in this variant. */
   {@param tags: ?}  /** list of tags for this entry, with "name" and "url" keys. */
   {@param diffTree: ?}  /** unused in this variant. */
   {@param rename: ?}  /** if this entry was a rename or a copy of the path, an object containg:
@@ -166,7 +165,6 @@
   {@param author: ?}  /** author information with at least "name" and "relativeTime" keys. */
   {@param committer: ?}  /** committer information with at least "time" and "relativeTime" keys. */
   {@param branches: ?}  /** list of branches for this entry, with "name" and "url" keys. */
-  {@param parents: ?}  /** unused in this variant. */
   {@param tags: ?}  /** list of tags for this entry, with "name" and "url" keys. */
   {@param diffTree: ?}  /** unused in this variant. */
   {@param rename: ?}  /** if this entry was a rename or a copy of the path, an object containg:
@@ -194,7 +192,6 @@
   {@param author: ?}  /** author information with at least "name" and "relativeTime" keys. */
   {@param committer: ?}  /** committer information with at least "time" and "relativeTime" keys. */
   {@param branches: ?}  /** list of branches for this entry, with "name" and "url" keys. */
-  {@param parents: ?}  /** unused in this variant. */
   {@param tags: ?}  /** list of tags for this entry, with "name" and "url" keys. */
   {@param diffTree: ?}  /** unused in this variant. */
   {@param rename: ?}  /** if this entry was a rename or a copy of the path, an object containg: