This commit removes the header template files opensslconf.h as it is not
a generated header anymore (configuration.h is the generated header
now).

The motivation for this is that not using opensslconf.h from the OpenSSL
include directory means an addon that includes openssl/ssl.h will get
the following error:

~/.cache/node-gyp/17.8.0/include/node/openssl/macros.h:148:4: error:
 compatibility level"
  148 | #  error "The requested API level higher than the configured
 API compatibility level"

For more details please see #40575.

Fixes: #40575