Fix issue mentioned in 55980c6fb with Javascript spazzing out on Flash
posts and randomly triggering keyboard shortcuts.
The bug was calling `javascript_pack_tag` twice. This caused the
runtime Javascript chunk to be loaded twice, caused a lot of Javascript
errors that somehow resulted in keyboard shortcuts being triggered.
The fix is to combine both calls into `javascript_pack_tag "application", "flash"`.
hxxps://github.com.rails.webpacker.issues.2932
fff68e1d16