Update mongodb Docker tag to v15.6.3

[renovate[bot]]

This PR contains the following updates:

Package	Update	Change
mongodb (source)	patch	15.6.1 -> 15.6.3

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Release Notes

bitnami/charts (mongodb)

### [`v15.6.3`](https://togithub.com/bitnami/charts/blob/HEAD/bitnami/mongodb/CHANGELOG.md#1563-2024-06-04) - \[bitnami/mongodb] Bump chart version ([#​26650](https://togithub.com/bitnami/charts/pull/26650))

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