Prefer environment variables to the `REVISION` file

Changed

• Use the revision set by Heroku, Render, Kamal or Scalingo when the application also has a REVISION file. Since version 4.6.0, a REVISION file took precedence over the HEROKU_SLUG_COMMIT, RENDER_GIT_COMMIT, KAMAL_VERSION and CONTAINER_VERSION environment variables, so an application that kept a placeholder REVISION file in source control reported that placeholder as its revision. The revision config option and the APP_REVISION environment variable still take precedence over both.

  Thanks to @rmm5t for their contribution!

Changed

• Update appsignal dependency to 5.0.2.

View the Ruby gem v5.0.2 changelog for more information.