Clear _cacheInvalid flag after rebuilding limiter cache in DefaultPar…

…titionedRateLimiter (#98075)

Fix #95611

src/libraries/System.Threading.RateLimiting/src/System/Threading/RateLimiting/DefaultPartitionedRateLimiter.cs

@@ -218,6 +218,7 @@ private async Task Heartbeat()
                 {
                     _cachedLimiters.Clear();
                     _cachedLimiters.AddRange(_limiters);
+                    _cacheInvalid = false;
                 }
             }