utils: remove unused IContextMenuTargets

This is no longer used since refactoring to use function components.

src/utils/IContextMenuTarget.ts

@@ -1,45 +0,0 @@
-// SPDX-License-Identifier: MIT
-// Copyright (c) 2021 The Pybricks Authors
-//
-// Alternative to @blueprintjs/core ContextMenuTarget decorator.
-
-import { ContextMenu } from '@blueprintjs/core';
-
-export interface IContextMenuTarget {
-    renderContextMenu(): JSX.Element;
-    onContextMenuClose(): void;
-}
-
-export function handleContextMenu(
-    event: React.MouseEvent,
-    target: IContextMenuTarget,
-): void {
-    // istanbul ignore if: not expected
-    if (event.defaultPrevented) {
-        return;
-    }
-
-    event.preventDefault();
-
-    const listener = (e: KeyboardEvent) => {
-        if (e.key === 'Escape') {
-            // istanbul ignore if: not expected
-            if (e.defaultPrevented) {
-                return;
-            }
-
-            e.preventDefault();
-            ContextMenu.hide();
-        }
-    };
-    window.addEventListener('keydown', listener);
-
-    ContextMenu.show(
-        target.renderContextMenu(),
-        { left: event.clientX, top: event.clientY },
-        () => {
-            window.removeEventListener('keydown', listener);
-            target.onContextMenuClose();
-        },
-    );
-}