Remove unused method com.google.protobuf.Protobuf.getTotalSchemaSize()

There appear to be no callers of this.

I'm removing this in preparation to try to offer a more performant
java.lang.ClassValue replacement for the ConcurrentHashMap.

Removing this method means I don't have to reimplement it for ClassValue.

PiperOrigin-RevId: 814272309

Author: mhansen

java/core/src/main/java/com/google/protobuf/Protobuf.java

@@ -115,14 +115,4 @@ public Schema<?> registerSchemaOverride(Class<?> messageType, Schema<?> schema)
   private Protobuf() {
     schemaFactory = new ManifestSchemaFactory();
   }
-
-  int getTotalSchemaSize() {
-    int result = 0;
-    for (Schema<?> schema : schemaCache.values()) {
-      if (schema instanceof MessageSchema) {
-        result += ((MessageSchema) schema).getSchemaSize();
-      }
-    }
-    return result;
-  }
 }