Clarify canUseTrackFlows comment with TODO for removal

Update the comment on the hardcoded canUseTrackFlows() gate to explain
what the track flows are and link to the tracking issue so we know to
remove this gate and its call sites when the new track flows feature
is complete.

Co-authored-by: Daniel Gale-Rosen <dangrous@users.noreply.github.com>

Author: MelvinBot

src/libs/Permissions.ts

@@ -29,7 +29,9 @@ function isBetaEnabled(beta: Beta, betas: OnyxEntry<Beta[]>, betaConfiguration?:
 }
 
 /**
- * Track flows are temporarily disabled.
+ * Track flows ("Share with my accountant", "Categorize it") are hardcoded off.
+ * TODO: Remove this gate and its call sites once the new track flows feature is complete.
+ * See: https://github.com/Expensify/Expensify/issues/504214
  */
 function canUseTrackFlows(): boolean {
     return false;