docs: add missing group id for tabs (#16196)

docs/src/intro-csharp.md

@@ -10,6 +10,7 @@ You can choose to use [NUnit base classes](./test-runners.md#nunit) or [MSTest b
 1. Start by creating a new project with `dotnet new`. This will create the `PlaywrightTests` directory which includes a `UnitTest1.cs` file:
 
 <Tabs
+  groupId="test-runners"
   defaultValue="nunit"
   values={[
     {label: 'NUnit', value: 'nunit'},
@@ -37,6 +38,7 @@ cd PlaywrightTests
 2. Install the necessary Playwright dependencies:
 
 <Tabs
+  groupId="test-runners"
   defaultValue="nunit"
   values={[
     {label: 'NUnit', value: 'nunit'},
@@ -76,6 +78,7 @@ pwsh bin\Debug\netX\playwright.ps1 install
 Edit the `UnitTest1.cs` file with the code below to create an example end-to-end test:
 
 <Tabs
+  groupId="test-runners"
   defaultValue="nunit"
   values={[
     {label: 'NUnit', value: 'nunit'},
@@ -160,6 +163,7 @@ public class UnitTest1 : PageTest
 By default tests will be run on Chromium. This can be configured via the `BROWSER` environment variable, or by adjusting the [launch configuration options](./test-runners.md). Tests are run in headless mode meaning no browser will open up when running the tests. Results of the tests and test logs will be shown in the terminal.
 
 <Tabs
+  groupId="test-runners"
   defaultValue="nunit"
   values={[
     {label: 'NUnit', value: 'nunit'},

docs/src/writing-tests-csharp.md

@@ -8,6 +8,7 @@ Playwright assertions are created specifically for the dynamic web. Checks are a
 Take a look at the example test below to see how to write a test using web first assertions, locators and selectors.
 
 <Tabs
+  groupId="test-runners"
   defaultValue="nunit"
   values={[
     {label: 'NUnit', value: 'nunit'},
@@ -117,6 +118,7 @@ await Expect(Page.Locator("text=Installation")).ToBeVisibleAsync();
 The Playwright NUnit and MSTest test framework base classes will isolate each test from each other by providing a separate `Page` instance. Pages are isolated between tests due to the Browser Context, which is equivalent to a brand new browser profile, where every test gets a fresh environment, even when multiple tests run in a single Browser.
 
 <Tabs
+  groupId="test-runners"
   defaultValue="nunit"
   values={[
     {label: 'NUnit', value: 'nunit'},
@@ -169,6 +171,7 @@ public class UnitTest1 : PageTest
 You can use `SetUp`/`TearDown` in NUnit or `TestInitialize`/`TestCleanup` in MSTest to prepare and clean up your test environment:
 
 <Tabs
+  groupId="test-runners"
   defaultValue="nunit"
   values={[
     {label: 'NUnit', value: 'nunit'},