chore: update prettier php plugin in owlbot (#8614)

Author: bshaffer

owlbot.py

@@ -46,7 +46,7 @@
  'npm',
  'exec',
  '--yes',
- '--package=@prettier/plugin-php@^0.16',
+ '--package=@prettier/plugin-php@^0.19',
  '--',
  'prettier',
  '**/Client/*',