fix(spanner): use a mutable set for built-in metric attribute filters

Author: rahul2393

java-spanner/google-cloud-spanner/src/main/java/com/google/cloud/spanner/BuiltInMetricsConstant.java

@@ -297,7 +297,7 @@ private static Set<String> baseAttributesFilter(boolean includeEndpointAttribute
     Set<String> attributesFilter =
         BuiltInMetricsConstant.COMMON_ATTRIBUTES.stream()
             .map(AttributeKey::getKey)
-            .collect(Collectors.toSet());
+            .collect(Collectors.toCollection(HashSet::new));
     if (includeEndpointAttribute) {
       attributesFilter.add(ENDPOINT_KEY.getKey());
     }