Add java.util.Properties to WellKnownThreadSafety.

PiperOrigin-RevId: 959124000

Author: java-team-github-bot

core/src/main/java/com/google/errorprone/bugpatterns/threadsafety/WellKnownThreadSafety.java

@@ -67,6 +67,7 @@ private static ImmutableMap<String, AnnotationInfo> buildThreadSafeClasses(
         .add(java.lang.Thread.class)
         .add(java.time.InstantSource.class)
         .add(java.time.Clock.class)
+        .add(java.util.Properties.class)
         .add(java.util.Random.class)
         .add(java.util.concurrent.atomic.AtomicBoolean.class)
         .add(java.util.concurrent.atomic.AtomicInteger.class)