replace RemoveWhere extension with equivalent HashSet methods

docs/release-notes.md

@@ -3,6 +3,7 @@
 # Release notes
 ## Upcoming release
 * For players:
+  * Improved performance.
   * Improved error message when a mod is blocked by Windows Smart App Control.
 
 ## 4.5.2

src/SMAPI/Framework/Input/SInputState.cs

@@ -95,8 +95,8 @@ internal sealed class SInputState : InputState
             if (this.CustomPressedKeys.Count > 0 || this.CustomReleasedKeys.Count > 0)
             {
                 // reset overrides that no longer apply
-                this.CustomPressedKeys.RemoveWhere(key => reallyDown.Contains(key));
-                this.CustomReleasedKeys.RemoveWhere(key => !reallyDown.Contains(key));
+                this.CustomPressedKeys.ExceptWith(reallyDown);
+                this.CustomReleasedKeys.IntersectWith(reallyDown);
 
                 // apply overrides
                 if (this.ApplyOverrides(this.CustomPressedKeys, this.CustomReleasedKeys, controller, keyboard, mouse))