Re-enable prettier for compiler/

Now that the compiler directory has its own prettier config, we can
remove the prettierignore entry for compiler/ so it still runs in your
editor if you open the root directory

ghstack-source-id: aeef8fedf3bac7c81a81d5bec5bc32100da65174
Pull Request resolved: #29993

.prettierignore

@@ -1,6 +1,5 @@
 build
 
-compiler
 packages/react-devtools-core/dist
 packages/react-devtools-extensions/chrome/build
 packages/react-devtools-extensions/firefox/build