[bugfix] Treat input throughput data as immutable

[rbroggi]

Which problem is this PR solving?

• Immutability bug discovered in PR Issue #3349 - enable -shuffle=on in tests #3350

Short description of the changes

• correct slight immutability issue discovered while enabling test shuffling

[codecov]

Codecov Report

Merging #3360 (37d7f34) into master (e6b1c8f) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3360      +/-   ##
==========================================
+ Coverage   96.47%   96.49%   +0.01%     
==========================================
  Files         259      259              
  Lines       15166    15178      +12     
==========================================
+ Hits        14632    14646      +14     
+ Misses        451      449       -2     
  Partials       83       83              

Impacted Files	Coverage Δ
...lugin/sampling/strategystore/adaptive/processor.go	100.00% <100.00%> (ø)
pkg/config/tlscfg/cert_watcher.go	94.73% <0.00%> (+2.10%)	⬆️

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