Switch to 'npx' for lint-staged in pre-commit hook (#3658)

This way we get rid of the script entry in the `package.json` and the
whole thing becomes a little less complex.

.husky/pre-commit

@@ -1,5 +1,5 @@
 #!/bin/sh
 
-if command -v npm &> /dev/null; then
-  npm run lint:staged
+if command -v npx &> /dev/null; then
+  npx lint-staged
 fi