chore: remove typedoc.json file (#4112)

* The docs are generated using `Dgeni` and the `typedoc.json` file is
therefore unused and can be removed.

src/lib/typedoc.json

@@ -1,20 +0,0 @@
-{
-  "mode": "modules",
-  "out": "./dist/api",
-  "json": "./dist/api/api.json",
-  "theme": "default",
-  "experimentalDecorators": "true",
-  "emitDecoratorMetadata": "true",
-  "excludePrivate": "true",
-  "excludeExternals": "true",
-  "includeDeclarations": "true",
-  "target": "ES6",
-  "exclude": "**/+(*.spec.ts|*.scss|*.html)",
-  "name": "Angular Material",
-  "moduleResolution": "node",
-  "preserveConstEnums": "true",
-  "stripInternal": "true",
-  "suppressExcessPropertyErrors": "true",
-  "suppressImplicitAnyIndexErrors": "true",
-  "module": "commonjs"
-}