chore(mongodb): update image docker.io/bitnamisecure/mongodb digest to bc7b21c (#46035)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| docker.io/bitnamisecure/mongodb | digest | `fc0e9e2` → `bc7b21c` |

---

> [!WARNING]
> Some dependencies could not be looked up. Check the [Dependency
Dashboard](../issues/18710) for more information.

Add the preset `:preserveSemverRanges` to your config if you don't want
to pin your dependencies.

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Enabled.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR has been generated by [Renovate
Bot](https://redirect.github.com/renovatebot/renovate).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My4yOS4yIiwidXBkYXRlZEluVmVyIjoiNDMuMjkuMiIsInRhcmdldEJyYW5jaCI6Im1hc3RlciIsImxhYmVscyI6WyJhcHAvbW9uZ29kYiIsImF1dG9tZXJnZSIsInJlbm92YXRlL2NvbnRhaW5lciIsInR5cGUvZGlnZXN0Il19-->

charts/stable/mongodb/Chart.yaml

@@ -43,5 +43,5 @@ sources:
   - https://hub.docker.com/r/bitnamisecure/mongodb
   - https://www.mongodb.com
 type: application
-version: 16.18.2
+version: 16.18.3
 

charts/stable/mongodb/values.yaml

@@ -2,7 +2,7 @@
 image:
   repository: docker.io/bitnamisecure/mongodb
   pullPolicy: IfNotPresent
-  tag: latest@sha256:fc0e9e2c8191dc074d25cd1d0ff501141bc08a82b9607f3cd4217c04e6cb3ba7
+  tag: latest@sha256:bc7b21cd9f840fd5bc4bc731f3eac0012700cb17a9c4bd95301752f35365354c
 
 workload:
   main: