Remove “% Charset: ...” comments from locale sources

These comments are useless and only confusing.  The encodings used to
create binary locales from source locales are listed in the
localedata/SUPPORTED file.  The source files itself are ASCII or UTF-8
encoded where non-ASCII UTF-8 is currently only used in comments. If
all locale source files are UTF-8 anyway, there is no need to specify
that in a special comment.