refactor(docs-infra): remove example configs for tooling that no longer exists

An example-config.json marked a directory as a doc example and told aio's
example tooling which boilerplate to use and what to run against it. #56496
removed that tooling in June 2024. Eight of these fifteen files are empty and no
code has read any of them since; the name survives only in the zip and
StackBlitz exclude lists, which skip it rather than open it.

(cherry picked from commit ddfd8a8e9b)

adev/src/content/examples/angular-compiler-options/example-config.json

@@ -1,10 +0,0 @@
-{
-  "projectType": "cli",
-  "overrideBoilerplate": ["tsconfig.json", "tsconfig.app.json"],
-  "tests": [
-    {
-      "cmd": "yarn",
-      "args": ["e2e"]
-    }
-  ]
-}

adev/src/content/examples/elements/example-config.json

@@ -1,3 +0,0 @@
-{
-  "projectType": "elements"
-}

adev/src/content/examples/forms-overview/example-config.json

@@ -1,6 +0,0 @@
-{
-  "tests": [
-    {"cmd": "yarn", "args": ["test", "--browsers=ChromeHeadlessNoSandbox", "--no-watch"]},
-    {"cmd": "yarn", "args": ["e2e", "--configuration=production"]}
-  ]
-}

adev/src/content/examples/i18n/example-config.json

@@ -1,10 +0,0 @@
-{
-  "projectType": "i18n",
-  "overrideBoilerplate": ["angular.json"],
-  "tests": [
-    {
-      "cmd": "yarn",
-      "args": ["e2e"]
-    }
-  ]
-}

adev/src/content/examples/schematics-for-libraries/example-config.json

@@ -1,3 +0,0 @@
-{
-  "projectType": "schematics"
-}

adev/src/content/examples/service-worker-getting-started/example-config.json

@@ -1,25 +0,0 @@
-{
-  "projectType": "service-worker",
-  "tests": [
-    {"cmd": "yarn", "args": ["e2e"]},
-    {"cmd": "yarn", "args": ["build"]},
-    {
-      "cmd": "node",
-      "args": ["--eval", "assert(fs.existsSync('./dist/ngsw.json'), 'ngsw.json is missing')"]
-    },
-    {
-      "cmd": "node",
-      "args": [
-        "--eval",
-        "assert(fs.existsSync('./dist/ngsw-worker.js'), 'ngsw-worker.js is missing')"
-      ]
-    },
-    {
-      "cmd": "node",
-      "args": [
-        "--eval",
-        "assert(require('./package.json').dependencies['@angular/service-worker'], '@angular/service-worker is missing')"
-      ]
-    }
-  ]
-}

adev/src/content/examples/v21-game-world/example-config.json

@@ -1,6 +0,0 @@
-{
-  "tests": [
-    {"cmd": "yarn", "args": ["test", "--browsers=ChromeHeadlessNoSandbox", "--no-watch"]},
-    {"cmd": "yarn", "args": ["e2e", "--configuration=production"]}
-  ]
-}