utils/fallbacksrc: Remove custom source elements from internal bin when shutting down

Otherwise we can't add it again later to a new bin when starting up again.
11 jobs for master in 14 minutes and 53 seconds (queued for 18 seconds)
Status Job ID Name Coverage
  Prep
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build-1-41

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build-nightly

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build-stable

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  Lint
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check commits

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rustfmt

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  Test
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test 1.41

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test nightly

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test stable

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  Extras
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clippy

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deny

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outdated

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