[Bug] Add warning and hint for legacy metrics

[qrtt1]

PR checklist

• Ensure you have added or ran the appropriate tests for your PR.
• DCO signed

What type of PR is this?

bugfix

What this PR does / why we need it:

After dbt 1.6 the legacy metrics are no longer supported, users should migrate to the MetricFlow

Which issue(s) this PR fixes:

sc-32180

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[codecov]

Codecov Report

Merging #867 (3833414) into main (9ae345d) will increase coverage by 0.05%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##             main     #867      +/-   ##
==========================================
+ Coverage   47.82%   47.88%   +0.05%     
==========================================
  Files          71       71              
  Lines        9994    10003       +9     
==========================================
+ Hits         4780     4790      +10     
+ Misses       5214     5213       -1     

Files Changed	Coverage Δ
piperider_cli/compare_report.py	31.52% <88.88%> (+1.43%)	⬆️

... and 1 file with indirect coverage changes

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