Remove redundant Namespace to align netfx/netcore

[MichelZ]

An easy to review change that removes redundant namespace definitions to align netfx/netcore

Part of #2953

[benrr101]

I'm surprised there aren't more instances in this file...

[cheenamalhotra]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 72.32%. Comparing base (9d5ca32) to head (675f7fe).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
...nt/netfx/src/Microsoft/Data/SqlClient/TdsParser.cs	0.00%	9 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2960   +/-   ##
=======================================
  Coverage   72.31%   72.32%           
=======================================
  Files         288      288           
  Lines       59660    59660           
=======================================
+ Hits        43145    43147    +2     
+ Misses      16515    16513    -2     

Flag	Coverage Δ
addons	92.58% <ø> (ø)
netcore	75.41% <ø> (-0.01%)	⬇️
netfx	70.70% <0.00%> (+0.01%)	⬆️

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