Fix documentation formatting in preview.md

Enclose the task config example in code block so that the formatting of
the file does not change on the UI.

Change-Id: I70973db4c201f1f36b93b1b36ed0a2ac52ecd60e

src/main/resources/Documentation/test/preview.md

diff --git a/src/main/resources/Documentation/test/preview.md b/src/main/resources/Documentation/test/preview.md
index ec5967f..df25a6e 100644
--- a/src/main/resources/Documentation/test/preview.md
+++ b/src/main/resources/Documentation/test/preview.md
@@ -1,3 +1,4 @@
+```
 [root "INVALIDS Preview"]
   subtasks-file = invalids.config
 
@@ -629,3 +630,4 @@
       }
    ]
 }
+```

test/check_task_statuses.sh

diff --git a/test/check_task_statuses.sh b/test/check_task_statuses.sh
index c1639f5..6a6c475 100755
--- a/test/check_task_statuses.sh
+++ b/test/check_task_statuses.sh
@@ -184,7 +184,7 @@
 strip_non_invalid < "$EXPECTED".applicable > "$EXPECTED".invalid-applicable
 
 
-preview_pjson=$(echo "$DOC_PREVIEW" | testdoc_2_pjson)
+preview_pjson=$(example "$DOC_PREVIEW" 1 | testdoc_2_pjson)
 echo "$preview_pjson" | remove_suites "invalid" "secret" | \
     ensure json_pp > "$EXPECTED".preview-non-secret
 echo "$preview_pjson" | remove_suites "invalid" "!secret" | \
@@ -192,7 +192,7 @@
 echo "$preview_pjson" | remove_suites "secret" "!invalid" | \
     strip_non_invalid > "$EXPECTED".preview-invalid
 
-echo "$DOC_PREVIEW" | testdoc_2_cfg | replace_user > "$ROOT_CFG"
+example "$DOC_PREVIEW" 1 | testdoc_2_cfg | replace_user > "$ROOT_CFG"
 cnum=$(create_repo_change "$ALL" "$REMOTE_ALL" "$REF_ALL")
 PREVIEW_ROOTS=$(config_section_keys "root")