Remove unnecessary getExtension adapter

Author: winstliu

src/vscodeAdapter.ts

@@ -982,7 +982,6 @@ export interface vscode {
         onDidChangeConfiguration: Event<ConfigurationChangeEvent>;
     };
     extensions: {
-        getExtension(extensionId: string): Extension<any> | undefined;
         all: ReadonlyArray<Extension<any>>;
     };
     Uri: {

test/unitTests/features/reportIssue.test.ts

@@ -50,14 +50,6 @@ suite(`${reportIssue.name}`, () => {
 
     setup(() => {
         vscode = getFakeVsCode();
-        vscode.extensions.getExtension = () => {
-            return {
-                packageJSON: {
-                    version: csharpExtVersion
-                },
-                id: ""
-            };
-        };
 
         vscode.env.clipboard.writeText = (body: string) => {
             issueBody = body;

test/unitTests/testAssets/Fakes.ts

@@ -134,9 +134,6 @@ export function getFakeVsCode(): vscode.vscode {
             }
         },
         extensions: {
-            getExtension: () => {
-                throw new Error("Not Implemented");
-            },
             all: []
         },
         Uri: {