Mark the timestamptz variant of date_bin() as stable

Previously, it was immutable by lack of marking. This is not
correct, since the time zone could change.

Bump catversion

Discussion: https://www.postgresql.org/message-id/CAFBsxsG2UHk8mOWL0tca%3D_cg%2B_oA5mVRNLhDF0TBw980iOg5NQ%40mail.gmail.com
Backpatch to v14, when this function came in

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202107181
+#define CATALOG_VERSION_NO	202108311
 
 #endif

src/include/catalog/pg_proc.dat

@@ -5844,7 +5844,7 @@
   proargtypes => 'interval timestamp timestamp', prosrc => 'timestamp_bin' },
 { oid => '6178',
   descr => 'bin timestamp with time zone into specified interval',
-  proname => 'date_bin', prorettype => 'timestamptz',
+  proname => 'date_bin', provolatile => 's', prorettype => 'timestamptz',
   proargtypes => 'interval timestamptz timestamptz',
   prosrc => 'timestamptz_bin' },