Replace enable_context with enable-context in docs

So that it matches the parameter name as implemented in back-end.

Change-Id: I670a2bbae5c9e939e3edcfbd4332091b30419284
diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index cdf576c..c9d2ebb 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -2046,7 +2046,7 @@
 comments for each path are sorted by patch set number. Each comment has
 the `patch_set` and `author` fields set.
 
-If the `enable_context` request parameter is set to true, the comment entries
+If the `enable-context` request parameter is set to true, the comment entries
 will contain a list of link:#context-line[ContextLine] containing the lines of
 the source file where the comment was written.
 
@@ -6693,7 +6693,7 @@
 this comment applies.
 |`context_lines` |optional|
 A list of link:#context-line[ContextLine] containing the lines of the source
-file where the comment was written. Available only if the "enable_context"
+file where the comment was written. Available only if the "enable-context"
 parameter (see link:#list-change-comments[List Change Comments]) is set.
 
 |===========================