openssl: Fix CA fallback logic for OpenSSL 3.0 build

Prior to this change I assume a build error would occur when
CURL_CA_FALLBACK was used.

Closes https://github.com/curl/curl/pull/5587

lib/vtls/openssl.c

@@ -3024,7 +3024,7 @@ static CURLcode ossl_connect_step1(struct connectdata *conn, int sockindex)
 #endif
 
 #ifdef CURL_CA_FALLBACK
-  else if(verifypeer) {
+  if(verifypeer && !ssl_cafile && !ssl_capath) {
     /* verifying the peer without any CA certificates won't
        work so use openssl's built in default as fallback */
     SSL_CTX_set_default_verify_paths(backend->ctx);