Increase memory available for AP xml parser

[galitskiy]

Proposed changes

Increase memory available for xml parser in order to avoid potential issues with big policies.
https://docs.nginx.com/nginx-app-protect/admin-guide/install/#:~:text=file.%20The%20number-,471859200,-should%20be%20enough

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto master
• I will ensure my PR is targeting the master branch and pulling from my branch from my own fork

[codecov-commenter]

Codecov Report

Merging #2455 (465dfbe) into main (143b9b2) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2455   +/-   ##
=======================================
  Coverage   53.49%   53.49%           
=======================================
  Files          49       49           
  Lines       14314    14314           
=======================================
  Hits         7657     7657           
  Misses       6414     6414           
  Partials      243      243           

Impacted Files	Coverage Δ
internal/nginx/manager.go	0.00% <ø> (ø)

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