Fixes OSCP->OCSP typo in ocsp command line

Fixes OSCP->OCSP typo in ocsp command line

The existing help text says:

>  -badsig                 Corrupt last byte of loaded OSCP response signature (for test)

but this should be OCSP. This is the only occurrence within the project
of this typo.

CLA: trivial

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18684)

(cherry picked from commit 2837b19fcba4bf4ff2ecdc8435c650bf18c27552)