Fix OneBranch Build of msquictest

[nibanks]

Description

Fixes the following OneBranch build error of Windows user mode:

C:\__w\1\s\src\test\bin\quic_gtest.cpp(92,41): error C2065: 'QUIC_EXECUTION_CONFIG_FLAG_XDP': undeclared identifier [C:\__w\1\s\build\windows\x64_schannel\src\test\bin\msquictest.vcxproj]

This happens because internally we don't build test code with preview features enabled.

Testing

Need to run through the CI.

Documentation

N/A

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.13%. Comparing base (3c1a841) to head (ee84e84).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4688      +/-   ##
==========================================
+ Coverage   87.09%   87.13%   +0.04%     
==========================================
  Files          56       56              
  Lines       17361    17361              
==========================================
+ Hits        15120    15127       +7     
+ Misses       2241     2234       -7     

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