Address -Wunused-but-set-variable warning in examples (#1061)

Author: eramongodb

src/libmongoc/examples/client-side-encryption-schema-map.c

@@ -93,7 +93,7 @@ create_schema_file (bson_t *kms_providers,
    if (outfile) {
       fclose (outfile);
    }
-   return true;
+   return ret;
 }
 
 /* This example demonstrates how to use automatic encryption with a client-side
@@ -288,4 +288,4 @@ main (int argc, char **argv)
    bson_destroy (schema_map);
    mongoc_cleanup ();
    return exit_status;
-}
+}