Generate changelog to stdout

Since the changes aren't tracked in the single changelog.rst file,
generate the changelog to stdout instead, so it can be easily redirected
to the proper file.

contrib/gitchangelog/changelog.rc.py

@@ -291,12 +291,7 @@ include_merge = True
 #     r'/(?P<rev>[0-9]+\.[0-9]+(\.[0-9]+)?)\s+\([0-9]+-[0-9]{2}-[0-9]{2}\)\n--+\n/',
 #     idx=lambda m: m.start(1)
 # )
-# publish = stdout
-publish = FileInsertAtFirstRegexMatch(
-    "doc/arm/changelog.rst",
-    r"for changes relevant to them.\n\n",
-    idx=lambda m: m.end(0),
-)
+publish = stdout
 
 
 ## ``revs`` is a list of callable or a list of string