cobol: Fix up help.exp failures

cobol: Fix up help.exp failures

I'm seeing a new failure
FAIL: compiler driver --help=warnings option(s): "^ +-.*[^:.]\$" absent from output: "  -Wapply-commit              Warn if APPLY COMMIT is used "
after the last cobol/lang.opt changes.
The
make check-gcc RUNTESTFLAGS=help.exp
test verifies among other things that all the option descriptions
(which aren't omitted) are terminated with dot, so that they are consistent.
Seems most of the COBOL option descriptions violate this.

2025-12-03  Jakub Jelinek  <jakub@redhat.com>

	* lang.opt: Make sure all option descriptions are terminated with
	a dot.
	(preprocess): Capitalize first letter of option description.