Update nuspec on .net 6.0

[ErikEJ]

Update to #2303 (noticed while browsing the 5.2 release notes)

[ErikEJ]

@JRahnama FYI

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (838b931) 72.50% compared to head (389d27e) 72.45%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
...osoft/Data/SqlClient/Server/ValueUtilsSmi.netfx.cs	0.00%	2 Missing ⚠️
...qlClient/src/Microsoft/Data/SqlClient/SqlBuffer.cs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2317      +/-   ##
==========================================
- Coverage   72.50%   72.45%   -0.05%     
==========================================
  Files         310      310              
  Lines       61872    61873       +1     
==========================================
- Hits        44858    44832      -26     
- Misses      17014    17041      +27     

Flag	Coverage Δ
addons	92.88% <ø> (ø)
netcore	76.67% <66.66%> (-0.03%)	⬇️
netfx	69.86% <40.00%> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[JRahnama]

Thank you @ErikEJ.