Don't define functions in the prototype

If `VOID` is used, TypeScript is not able to figure out what the function parameters are.

Before:
```
$ npx tsc | wc -l
    1188
```

After:
```
$ npx tsc | wc -l
    1169
```

src/ol/renderer/Map.js

@@ -6,7 +6,7 @@ import Disposable from '../Disposable.js';
 import {listen, unlistenByKey} from '../events.js';
 import EventType from '../events/EventType.js';
 import {getWidth} from '../extent.js';
-import {TRUE, VOID} from '../functions.js';
+import {TRUE} from '../functions.js';
 import {visibleAtResolution} from '../layer/Layer.js';
 import {shared as iconImageCache} from '../style/IconImageCache.js';
 import {compose as composeTransform, invert as invertTransform, setFromArray as transformSetFromArray} from '../transform.js';
@@ -46,6 +46,13 @@ class MapRenderer extends Disposable {
 
   }
 
+  /**
+   * @abstract
+   * @param {import("../render/EventType.js").default} type Event type.
+   * @param {import("../PluggableMap.js").FrameState} frameState Frame state.
+   */
+  dispatchRenderEvent(type, frameState) {}
+
   /**
    * Register layer renderer constructors.
    * @param {Array<import("./Layer.js").default>} constructors Layer renderers.
@@ -283,6 +290,13 @@ class MapRenderer extends Disposable {
     }
   }
 
+  /**
+   * @abstract
+   * Render.
+   * @param {?import("../PluggableMap.js").FrameState} frameState Frame state.
+   */
+  renderFrame(frameState) {}
+
   /**
    * @param {import("../PluggableMap.js").FrameState} frameState Frame state.
    * @protected
@@ -317,20 +331,6 @@ function expireIconCache(map, frameState) {
 }
 
 
-/**
- * Render.
- * @param {?import("../PluggableMap.js").FrameState} frameState Frame state.
- */
-MapRenderer.prototype.renderFrame = VOID;
-
-
-/**
- * @param {import("../render/EventType.js").default} type Event type.
- * @param {import("../PluggableMap.js").FrameState} frameState Frame state.
- */
-MapRenderer.prototype.dispatchRenderEvent = VOID;
-
-
 /**
  * @param {import("../layer/Layer.js").State} state1 First layer state.
  * @param {import("../layer/Layer.js").State} state2 Second layer state.