chore(prettier): ignore lib/vscode (#5347)

We were using an overrides command in our `.prettierrc.yaml` which
quickly became out of sync with Code's Prettier styles.

Instead, we simply tell Prettier to ignore `lib/vscode`.

This way, if you have `formatOnSave` on and you save inside
`lib/vscode`, you won't convert the file to use code-server's styles.

.prettierignore

@@ -0,0 +1 @@
+lib/vscode

.prettierrc.yaml

@@ -4,14 +4,3 @@ trailingComma: all
 arrowParens: always
 singleQuote: false
 useTabs: false
-
-overrides:
-  # Attempt to keep VScode's existing code style intact.
-  - files: "lib/vscode/**/*.ts"
-    options:
-      # No limit defined upstream.
-      printWidth: 10000
-      semi: true
-      singleQuote: true
-      useTabs: true
-      arrowParens: avoid