gcore/doc: fix mistake in the gcore man page

The gcore man page says that the default prefix for a generated core
file will be 'gcore', i.e. we'll create files like 'gcore.pid'.  In
reality the default is 'core'.

As far as I can tell, the default has been 'core' for years, and the
docs used to say that the default was 'core', but the docs were
changed by mistake in commit:

  commit 129eb0f1f16dc7a49799a024a7bcb109d954a1e7
  Date:   Fri Jul 27 00:52:23 2018 -0400

      Improve gcore manpage and clarify "-o" option

So, lets bring the docs back inline with the code.

Approved-By: Tom Tromey <tom@tromey.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
1 file changed