fix: Fix variable name in error message for "unsupported data type" in rolling and upsampling operations

[MarcoGorelli]

closes #20081

Currently, the error message refers to window_size, but that's not correct, because ensure_duration_matches_dtype matches on the time/index column dtype

It's a little unfortunate that the name of this variable across operations:

• upsample: time_column
• rolling: index_column
• rolling_*_by: by

but I think referring to "temporal/index column" should be enough to clear up the confusion

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.00%. Comparing base (5f44997) to head (c2accef).
Report is 14 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20553      +/-   ##
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- Coverage   79.04%   79.00%   -0.04%     
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  Files        1564     1564              
  Lines      220640   220619      -21     
  Branches     2502     2502              
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- Hits       174404   174308      -96     
- Misses      45662    45737      +75     
  Partials      574      574              

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