feat: remove traffic_type in DownloadPeerDuration metric

[gaius-qi]

Description

• Remove traffic_type in DownloadPeerDuration metric.

Related Issue

Motivation and Context

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[hyy0322]

lgtm

[codecov]

Codecov Report

Merging #2357 (5334809) into main (acff931) will increase coverage by 49.68%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##           main    #2357       +/-   ##
=========================================
+ Coverage      0   49.68%   +49.68%     
=========================================
  Files         0      148      +148     
  Lines         0    19644    +19644     
=========================================
+ Hits          0     9761     +9761     
- Misses        0     9269     +9269     
- Partials      0      614      +614     

Flag	Coverage Δ
unittests	49.68% <100.00%> (?)

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

Impacted Files	Coverage Δ
scheduler/metrics/metrics.go	100.00% <ø> (ø)
scheduler/service/service_v1.go	79.38% <100.00%> (ø)
scheduler/service/service_v2.go	83.78% <100.00%> (ø)

... and 145 files with indirect coverage changes