Use the inherited 'bsd-gcc-shared' config on 32-bit x86 BSDs.

Use the inherited 'bsd-gcc-shared' config on 32-bit x86 BSDs.

BSD-generic32 already uses this for building shared libraries on other
32-bit BSD platforms.  Commit b7efa56 collapsed various *BSD targets
down to the BSD-generic ones and BSD-x86.  At the time only
OpenBSD/i386 used `bsd-shared` while both FreeBSD and NetBSD used
`bsd-gcc-shared`.  In practice, all of the BSDs are using either a
GCC/ld.bfd toolchain or a clang/lld toolchain both of which are
compatible with 'bsd-gcc-shared'.

Retire 'bsd-shared' since this removes the last user.

Fixes #12050.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Ben Kaduk <kaduk@mit.edu>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/12110)