i18n: fix coding tag unsupported by xgettext
Running `make update-pot` currently fails with the following error:
xgettext: mercurial/metadata.py:1: Unknown encoding "utf8". Proceeding with ASCII instead.
xgettext: Non-ASCII string at mercurial/metadata.py:311.
Please specify the source encoding through --from-code or through a comment
as specified in http://www.python.org/peps/pep-0263.html.
Differential Revision: https://phab.mercurial-scm.org/D9260
--- a/mercurial/metadata.py Thu Oct 29 11:11:54 2020 +0100
+++ b/mercurial/metadata.py Thu Oct 29 11:12:25 2020 +0100
@@ -1,4 +1,4 @@
-# coding: utf8
+# coding: utf-8
# metadata.py -- code related to various metadata computation and access.
#
# Copyright 2019 Google, Inc <martinvonz@google.com>