openssl: add two /* FALLTHROUGH */ to satisfy coverity

CID 1402159 and 1402158

lib/vtls/openssl.c

@@ -1746,10 +1746,12 @@ set_ssl_version_min_max(long *ctx_options, struct connectdata *conn,
 #if OPENSSL_VERSION_NUMBER >= 0x1000100FL
       *ctx_options |= SSL_OP_NO_TLSv1_1;
 #endif
+      /* FALLTHROUGH */
     case CURL_SSLVERSION_MAX_TLSv1_1:
 #if OPENSSL_VERSION_NUMBER >= 0x1000100FL
       *ctx_options |= SSL_OP_NO_TLSv1_2;
 #endif
+      /* FALLTHROUGH */
     case CURL_SSLVERSION_MAX_TLSv1_2:
     case CURL_SSLVERSION_MAX_DEFAULT:
 #ifdef TLS1_3_VERSION