UML-3753 tech debt - remove no longer needed IaP flag

[nickdavis2001]

Purpose

Remove tech debt by removing references to IaP flag thus simplifying the code, update tests

Approach

_Remove logic around IaP feature flag in code and tests, remove 3 front scenarios that are flagged to run only with the flag turned off, and steps that are only called by a scenario that is getting removed, api side remove feature flag logic from tests. remove flag from terraform. _

Checklist

• I have performed a self-review of my own code
• I have added relevant logging with appropriate levels to my code
• New event_codes have been documented on the wiki page
• I have updated documentation (Confluence/GitHub wiki/tech debt doc) where relevant
• I have added tests to prove my work
• I have added welsh translation tags and updated translation files
• I have run an accessibility tool on any pages I have made changes to and fixed any issues found
• I have notified the Interaction Designer of any content changes so that appropriate screenshots/flow diagram changes can be made
• The product team have tested these changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.90%. Comparing base (f00760a) to head (e8749f0).
Report is 189 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2987      +/-   ##
============================================
+ Coverage     91.25%   91.90%   +0.65%     
- Complexity     1504     1778     +274     
============================================
  Files           309      389      +80     
  Lines          6393     8232    +1839     
============================================
+ Hits           5834     7566    +1732     
- Misses          542      649     +107     
  Partials         17       17              

Flag	Coverage Δ
use-an-lpa-admin	78.85% <ø> (-0.41%)	⬇️
use-an-lpa-api	97.28% <ø> (-0.09%)	⬇️
use-an-lpa-front	90.69% <ø> (+1.15%)	⬆️

Files with missing lines	Coverage Δ
...i/app/src/App/src/Service/Lpa/SiriusLpaManager.php	99.08% <ø> (ø)

... and 218 files with indirect coverage changes