🐛 add missing useEffect dependency to dcc.Loading component

[KoolADE85]

This PR adds a missing dependency to the useEffect in the dcc.Loading component. This fixes a bug where it is possible for the loading spinner to be left enabled, even though loading has finished.

Fixes https://github.com/plotly/notebook-to-app/issues/1674

Note: I haven't been able to write a integration test that covers this code change precisely. The bug does not normally make an appearance - it's only in rare React race conditions that it is possible to get the "infinite loading bars".

@gvwilson since this affects internal projects, I'd love to get your team's eyes on this so we could maybe do a patch release?

Contributor Checklist

• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR

optionals

• I have added entry in the CHANGELOG.md
• If this PR needs a follow-up in dash docs, community thread, I have mentioned the relevant URLS as follows
  • this GitHub #PR number updates the dash docs
  • here is the show and tell thread in Plotly Dash community

[T4rk1n]

💃

[ndrezn]

💃