Bump ubuntu from 16.04 to 26.04 in /environment/docker/baseimage

Bumps ubuntu from 16.04 to 26.04.

---
updated-dependencies:
- dependency-name: ubuntu
  dependency-version: '26.04'
  dependency-type: direct:production
...

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Author: dependabot[bot]

environment/docker/baseimage/indy-baseimage.ubuntu.dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:16.04
+FROM ubuntu:26.04
 LABEL maintainer="Hyperledger <hyperledger-indy@lists.hyperledger.org>"
 
 RUN apt-get update && apt-get dist-upgrade -y