Update composer Docker tag to v2.8.6 (#287)

| datasource | package  | from  | to    |
| ---------- | -------- | ----- | ----- |
| docker     | composer | 2.8.5 | 2.8.6 |

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Dockerfile

@@ -2,7 +2,7 @@ ARG NODE_MAJOR=20
 
 # Aliasing base images, so we can change just this, when needing to upgrade or pull base layers
 FROM ubuntu:22.04 AS base-distro
-FROM composer:2.8.5 AS composer
+FROM composer:2.8.6 AS composer
 
 FROM base-distro AS install-markdownlint
 ARG NODE_MAJOR