chore(agent): remove obsolete code and update directive (4/16)

[hahuja2]

This PR removes obsolete php5 code and updates the directive. PR: 4/16

[newrelic-php-agent-bot]

Test Suite	Status	Result
Multiverse	❌	0/8 passing
SOAK	❌	80/85 passing

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.27%. Comparing base (ae34b4f) to head (875592f).

Additional details and impacted files

@@                    Coverage Diff                     @@
##           remove-obsolete-php5-code    #1073   +/-   ##
==========================================================
  Coverage                      77.27%   77.27%           
==========================================================
  Files                            199      199           
  Lines                          28327    28327           
==========================================================
  Hits                           21890    21890           
  Misses                          6437     6437           

Flag	Coverage Δ
agent-for-php-7.2	77.47% <ø> (ø)
agent-for-php-7.3	77.49% <ø> (ø)
agent-for-php-7.4	77.36% <ø> (ø)
agent-for-php-8.0	76.56% <ø> (ø)
agent-for-php-8.1	76.88% <ø> (ø)
agent-for-php-8.2	76.50% <ø> (ø)
agent-for-php-8.3	76.50% <ø> (ø)
agent-for-php-8.4	76.52% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.