Update NoTargets sample version to avoid build warning

[MattKotsenas]

Update the NoTargets SDK version used by the NoTargets sample to avoid this warning during build:

MSBuildSdks\samples\NoTargets\SampleNoTargets\SampleNoTargets.csproj : warning MSB4240: Multiple versions of the same
SDK "Microsoft.Build.NoTargets" cannot be specified. The previously resolved SDK version "3.7.56" from location
"MSBuildSdks\src\NoTargets\Microsoft.Build.NoTargets.csproj" will be used and the version "3.7.0" will be ignored.
[MSBuildSdks\MSBuildSdks.sln]