Update docker.io/eclipse-mosquitto Docker tag to v2.0.20

No problems deploying Eclipse Mosquitto patch version to Proxmox VE K3s Kubernetes cluster via Flux V2 image reconciliation in a GitOps approach with dependency update facilitated by Mend's Renovate Bot.

This MR contains the following updates:

Release Notes

v2.0.20

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Broker:

• Fix QoS 1 / QoS 2 publish incorrectly returning "no subscribers".
  Closes #​3128.
• Open files with appropriate access on Windows. Closes #​3119.
• Don't allow invalid response topic values.
• Fix some strict protocol compliance issues. Closes #​3052.

Client library:

• Fix cmake build on OS X. Closes #​3125.

Build:

• Fix build on NetBSD

v2.0.19

Compare Source

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Security:

• Fix mismatched subscribe/unsubscribe with normal/shared topics.
• Fix crash on bridge using remapped topic being sent a crafted packet.

Broker:

• Fix assert failure when loading a persistence file that contains
  subscriptions with no client id.
• Fix local bridges being incorrectly expired when
  persistent_client_expiration is in use.
• Fix use of CLOCK_BOOTTIME for getting time. Closes #​3089.
• Fix mismatched subscribe/unsubscribe with normal/shared topics.
• Fix crash on bridge using remapped topic being sent a crafted packet.

Client library:

• Fix some error codes being converted to string as "unknown". Closes #​2579.
• Clear SSL error state to avoid spurious error reporting. Closes #​3054.
• Fix "payload format invalid" not being allowed as a PUBREC reason code.
• Don't allow SUBACK with missing reason codes.

Build:

• Thread support is re-enabled on Windows.