log a warning.

Author: rmehta19

gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/InstantiatingGrpcChannelProvider.java

@@ -518,7 +518,7 @@ ChannelCredentials createS2ASecuredChannelCredentials() {
       } catch (FileNotFoundException ignore) {
         // Fallback to plaintext-to-S2A connection on error.
         LOG.log(
-            Level.INFO,
+            Level.WARNING,
             "Cannot establish an mTLS connection to S2A due to error loading MTLS to MDS credentials, falling back to plaintext connection to S2A: "
                 + ignore.getMessage());
         return createPlaintextToS2AChannelCredentials(plaintextAddress);