[browser tests] [keybindings] Squash intermittent heisenbug

This one was tricky to find.

An exception would happen that failed the current test file, usually launch-preferences.spec.js,
only when running the full browser test suite. However, if that file was removed, the exception
would happen in another file, and another file...

Turns-out it's related to the vscode.json-language-features built-in extension and playing with
the package.json file.

It seems the problem is with the Language LinkProvider feature, and its usage by the
json-language-features extension. But I could not reproduce it outside of the test suite.

Here's what the exception looks-like:

root INFO   1) Launch Preferences
            "before all" hook in "Launch Preferences":
            Uncaught Error: Uncaught Error: There is no document for file:///home/<user>/theia/examples/browser/package.json

        Error: There is no document for file:///home/<user>/theia/examples/browser/package.json
            at LinkProviderAdapter.provideLinks (/home/<user>/theia/packages/plugin-ext/lib/plugin/languages/link-provider.js:31:35)
            at /home/<user>/theia/packages/plugin-ext/lib/plugin/languages.js:332:97
            at LanguagesExtImpl.withAdapter (/home/<user>/theia/packages/plugin-ext/lib/plugin/languages.js:123:20)
            at LanguagesExtImpl.$provideDocumentLinks (/home/<user>/theia/packages/plugin-ext/lib/plugin/languages.js:332:21)
            at /home/<user>/theia/packages/plugin-ext/lib/common/proxy-handler.js:91:71
            at processTicksAndRejections (node:internal/process/task_queues:96:5)
            at async RpcProtocol.handleRequest (/home/<user>/theia/packages/core/lib/common/message-rpc/rpc-protocol.js:167:28) (http://127.0.0.1:3000/vendors-node_modules_theia_monaco-editor-core_esm_vs_base_common_severity_js-node_modules_the-68fc42.js:1785)

I went with a simple fix: have the keybindings tests use an alternative file instad of package.json.

Signed-off-by: Marc Dumais <marc.dumais@ericsson.com>

examples/api-tests/src/keybindings.spec.js

@@ -73,7 +73,7 @@ describe('Keybindings', function () {
             when: 'false'
         }));
 
-        const editor = await editorManager.open(workspaceService.tryGetRoots()[0].resource.resolve('package.json'), {
+        const editor = await editorManager.open(workspaceService.tryGetRoots()[0].resource.resolve('webpack.config.js'), {
             mode: 'activate',
             selection: {
                 start: {
@@ -83,7 +83,6 @@ describe('Keybindings', function () {
             }
         });
         toTearDown.push(editor);
-
         const waitForCommand = new Deferred();
         toTearDown.push(commands.onWillExecuteCommand(e => waitForCommand.resolve(e.commandId)));
         keybindings.dispatchKeyDown({