Don't filter out PRs/issues that match the release tag date

[wagoodman]

There is an edge case where if an issue or PR close timestamp matches the same timestamp as the release the changelog is being generated for, then the PR/issue in question is filtered out:

[0000] DEBUG github owner="wagoodman" repo="chronicle-test" path="../chronicle-test"
[0000]  INFO since tag="v0.0.0" date="2022-03-23 20:24 UTC"
[0000]  INFO until tag="v0.1.0" commit="5d95ff3aba8b6619b59f85f24332bc3ab5b0ae11"
[0000] DEBUG total merged PRs discovered: 2
[0000] TRACE PR #2 filtered out: merged after 2022-03-23 20:19 UTC (merged 2022-03-23 20:19 UTC)
[0000] DEBUG PRs contributing to changelog: 1
[0000] DEBUG total closed issues discovered: 0
[0000] DEBUG issues contributing to changelog: 0
[0000]  INFO discovered changes: 1
[0000] DEBUG   └── added-feature: 1

The correct behavior (which this PR fixes) is to keep the edge PR/issue included in the list of changes:

[0000] DEBUG github owner="wagoodman" repo="chronicle-test" path="../chronicle-test"
[0000]  INFO since tag="v0.0.0" date="2022-03-23 20:24 UTC"
[0000]  INFO until tag="v0.1.0" commit="5d95ff3aba8b6619b59f85f24332bc3ab5b0ae11"
[0000] DEBUG total merged PRs discovered: 2
[0000] DEBUG PRs contributing to changelog: 2
[0000] DEBUG total closed issues discovered: 0
[0000] DEBUG issues contributing to changelog: 0
[0000]  INFO discovered changes: 2
[0000] DEBUG   └── added-feature: 2