Remove Prettier references from .prettierignore comments

https://claude.ai/code/session_016Zjse7g4xyEjdLH7aX1vpu

Author: claude

.prettierignore

@@ -1,5 +1,4 @@
-# Test case input files contain styled-components CSS in template literals.
-# The formatter incorrectly adds spaces inside CSS selectors (e.g. &:${expr} → &: ${expr}),
-# which changes CSS semantics. Exclude them from formatting.
+# oxfmt incorrectly adds spaces inside CSS selectors in template literals
+# (e.g. &:${expr} → &: ${expr}), which changes CSS semantics.
 test-cases/*.input.tsx
 src/__tests__/fixtures/