Manage prettier updates manually going forward (TurboWarp#2247)

Prettier updates that result in style changes result in cascading format
validation errors until all pull requests get rebased. It's not worth
the effort to follow every update. We'll do this manually when there's
some change we want.

Author: GarboMuffin

.github/dependabot.yml

@@ -4,3 +4,8 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+    ignore:
+      # Prettier updates that result in style changes result in cascading format validation
+      # errors until all pull requests get rebased. It's not worth the effort to follow
+      # every update. We'll do this manually when there's some change we want.
+      - dependency-name: prettier