create_help.pl treats <literal> as replaceable

I found it annoying that sql_help.c contains a literal parameter as a
translatable string.

The cause is that create_help.pl treats <literal>match</> as a
replaceable. The attached excludes literals from translatable strings.

By a quick look it seems to me that the "match" in "COPY.. HEADER
match" is the first and only instance of a literal parameter as of
PG15.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center