Fix composer advisory install-block breaking 7.3/7.4 mess-detector & phpstan builds

[kapilpandya22]

Problem

Build and deploy fails for the PHP 7.3 (and 7.4) magento-mess-detector
and magento-phpstan images at the composer install --prefer-dist step:

• magento/product-community-edition requires guzzlehttp/guzzle ^6.3.3,
  but all 6.x versions are flagged by security advisories and get dropped.
• magento/magento2-functional-testing-framework ^3.0 requires
  spomky-labs/otphp ^10.0, which is likewise dropped; the resolver then
  falls through to newer MFTF versions that require PHP > 7.4.

Root cause: Composer 2.7+ enables policy.advisories.block by default,
which refuses to install advisory-affected packages. The audit.ignore
config already present only applies to composer audit, not to install.

Fix

Add RUN composer config policy.advisories.block false before
composer install in the four affected Dockerfiles:

Root cause: Composer 2.7+ enables policy.advisories.block by default,
which refuses to install advisory-affected packages. The audit.ignore
config already present only applies to composer audit, not to install.

Fix

Add RUN composer config policy.advisories.block false before
composer install in the four affected Dockerfiles:

• magento-mess-detector/Dockerfile:7.3
• magento-mess-detector/Dockerfile:7.4
• magento-phpstan/Dockerfile:7.3
• magento-phpstan/Dockerfile:7.4

These are CI static-analysis images built against a pinned, legacy Magento
tree, so install-time advisory blocking adds no value here.