fix: invalid metadata command (#124)

Fixes the Invalid MetaData command that could happen if a user entered a
sql statement that contained `pg_catalog`, but was not an actual `psql`
metadata command. The matcher would then return an error, instead of
just trying to execute the sql statement that the user entered.

Fixes b/200041331

Author: olavloite

src/main/java/com/google/cloud/spanner/pgadapter/commands/InvalidMetaCommand.java

@@ -37,6 +37,8 @@ public Pattern getPattern() {
 
   @Override
   public String translate() {
-    throw new IllegalArgumentException("Unsupported Meta Command");
+    // Just try to use the sql statement that was either generated by psql or manually entered by
+    // the user.
+    return sql;
   }
 }