fix: Remove unreachable code in CometScanRule

[andygrove]

Which issue does this PR close?

N/A

Rationale for this change

Fix this compiler warning (introduced in #1975):

CometScanRule.scala:327: unreachable code due to variable pattern 'dt' on line 310

What changes are included in this PR?

How are these changes tested?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 57.92%. Comparing base (f09f8af) to head (14998bb).
⚠️ Report is 1154 commits behind head on main.

Files with missing lines	Patch %	Lines
...n/scala/org/apache/comet/rules/CometScanRule.scala	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2252      +/-   ##
============================================
+ Coverage     56.12%   57.92%   +1.79%     
- Complexity      976     1290     +314     
============================================
  Files           119      143      +24     
  Lines         11743    13336    +1593     
  Branches       2251     2385     +134     
============================================
+ Hits           6591     7725    +1134     
- Misses         4012     4356     +344     
- Partials       1140     1255     +115     

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[comphead]

Thanks @andygrove we probably should enable fatal warning for scala.

[comphead]

Filed #2254