[v16.x] build: remove redundant condition from common.gypi

Both paths for the condition being removed result in the same value being assigned to openssl_product. This condition was also problematic as it was testing a variable in the same scope which gyp/gyp-next currently does not support.

Refs: https://gyp.gsrc.io/docs/InputFormatReference.md#user_defined-variables Refs: https://github.com/nodejs/node-gyp/issues/2750 Refs: https://github.com/nodejs/node/pull/38633

This doesn't apply to Node.js 18 and later as the condition in question was removed by semver-major https://github.com/nodejs/node/pull/38512. I've erred on the side of keeping openssl_fips defined in case anything out there is referencing it.