Fix removePeripheralsFromCache to iterate the right things. (#26670)

We're using the things we get out of the iterator as keys into the cache; these
are not the values.

Author: bzbarsky-apple

src/platform/Darwin/BleConnectionDelegateImpl.mm

@@ -698,7 +698,7 @@ - (void)removePeripheralFromCache:(CBPeripheral *)peripheral
 
 - (void)removePeripheralsFromCache
 {
-    for (CBPeripheral * peripheral in [_cachedPeripherals allValues]) {
+    for (CBPeripheral * peripheral in [_cachedPeripherals allKeys]) {
         [self removePeripheralFromCache:peripheral];
     }
 }