Release ink! 3.0.0-rc4 (#864)

* Add `Fixed` entry for #842

* Replace `3.0.0-rc3` with `3.0.0-rc4`

* Add bump allocator to release notes
19 jobs for v3.0.0-rc4 in 15 minutes and 12 seconds (queued for 3 seconds)
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ink-waterfall Ink Waterfall

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Triggered pipeline status is failed
Something's broken in: "https://gitlab.parity.io/parity/ink-waterfall/-/pipelines/148747"
Cleaning up file based variables
ERROR: Job failed: command terminated with exit code 1