Update docs. MTP: Option '--report-spekt-junit' expects at most 1 argument #233

The error is caused by MSBuild, not MTP. When dotnet test processes arguments after --, MSBuild treats semicolons as list separators and splits key1=value1;key2=value2 into two tokens before MTP even sees them.

The fix is to escape the semicolons when invoking: dotnet test -- --report-spekt-junit key1=value1%3Bkey2=value2

%3B is the URL-encoded semicolon that MSBuild passes through literally. MTP then receives the single string key1=value1;key2=value2 and the existing parsing code handles it correctly.

Configuration:
.NET 8
TestingPlatformDotnetTestSupport=true (VSTest mode)