pgm-index: Move prolog utils to separate, deprecated, section

Release-Notes: skip
Change-Id: I91ba14dceb51d21a18682aa98840bd3a7275f34e

Documentation/pgm-index.txt

diff --git a/Documentation/pgm-index.txt b/Documentation/pgm-index.txt
index 8f4cbda..e8f5865 100644
--- a/Documentation/pgm-index.txt
+++ b/Documentation/pgm-index.txt
@@ -15,18 +15,12 @@
 link:pgm-daemon.html[daemon]::
 	Gerrit HTTP, SSH network server.
 
-link:pgm-prolog-shell.html[prolog-shell]::
-	Simple interactive Prolog interpreter.
-
 link:pgm-reindex.html[reindex]::
 	Rebuild the secondary index.
 
 link:pgm-SwitchSecureStore.html[SwitchSecureStore]::
 	Change used SecureStore implementation.
 
-link:pgm-rulec.html[rulec]::
-	Compile project-specific Prolog rules to JARs.
-
 version::
 	Display the release version of Gerrit Code Review.
 
@@ -44,6 +38,14 @@
 link:pgm-MigrateAccountPatchReviewDb.html[MigrateAccountPatchReviewDb]::
 	Migrates AccountPatchReviewDb from one database backend to another.
 
+=== Prolog Utilities (DEPRECATED)
+
+link:pgm-prolog-shell.html[prolog-shell]::
+	Simple interactive Prolog interpreter.
+
+link:pgm-rulec.html[rulec]::
+	Compile project-specific Prolog rules to JARs.
+
 GERRIT
 ------
 Part of link:index.html[Gerrit Code Review]