Remove Apollo error suppression feature flag

What does this MR do and why?

Remove Apollo error suppression feature flag

This removes the suppress_apollo_errors_during_navigation feature flag, as it's been enabled in production without issue for a week.

Addresses #342745 (closed) and #335530 (closed).

Screenshots or screen recordings

See !72031 (merged).

How to set up and validate locally

See !72031 (merged), although now of course the feature flag is removed, so the new behaviour should always happen.

MR acceptance checklist

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