Fix a warning related to regular expression in AppSec

[y9v]

What does this PR do?
It fixes a following warning:

dd-trace-rb/lib/datadog/appsec/actions_handler/serializable_backtrace.rb:14: warning: character class has duplicated range: /\b([\w+:{2}]*\w+)?[#|.]?\b(\w+)\z/

Motivation:
We don't want any warnings to be triggered by our library code.

Change log entry
None. This change is internal.

Additional Notes:
None.

How to test the change?

ruby -W lib/datadog/appsec/actions_handler/serializable_backtrace.rb

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.77%. Comparing base (e239a85) to head (48f0a70).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4548      +/-   ##
==========================================
- Coverage   97.77%   97.77%   -0.01%     
==========================================
  Files        1392     1392              
  Lines       84981    84981              
  Branches     4287     4287              
==========================================
- Hits        83093    83086       -7     
- Misses       1888     1895       +7     

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[datadog-datadog-prod-us1]

Datadog Report

Branch report: appsec-fix-regex-warning
Commit report: 48f0a70
Test service: dd-trace-rb

✅ 0 Failed, 20784 Passed, 1373 Skipped, 3m 17.88s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-03-31 08:53:34

Comparing candidate commit 48f0a70 in PR branch appsec-fix-regex-warning with baseline commit e239a85 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.

[p-datadog]

👍 LGTM