fix: Memory leak introduced by correlation between metrics & traces fixed

[dadrus]

Related issue(s)

closes #448 and reverts tracing and metrics correlation introduced in #359

Checklist

• I agree to follow this project's Code of Conduct.
• I have read, and I am following this repository's Contributing Guidelines.
• I have read the Security Policy.
• I have referenced an issue describing the bug/feature request.
• I have added tests that prove the correctness of my implementation.
• I have updated the documentation.

Description

Correlating metrics and traces was a very bad idea!

[codecov]

Codecov Report

Merging #449 (2dba8bb) into main (4213d27) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #449      +/-   ##
==========================================
- Coverage   88.20%   88.17%   -0.03%     
==========================================
  Files         200      200              
  Lines        8069     8053      -16     
==========================================
- Hits         7117     7101      -16     
  Misses        780      780              
  Partials      172      172              

Impacted Files	Coverage Δ
internal/fiber/middleware/prometheus/handler.go	100.00% <100.00%> (ø)

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