[PWGDQ] fix swapped covariance values

[harvastum]

this fixes swapped covariances in mftMchMatcher.cxx

fwdmatchcandidates::CXYMCH, // X - Y,
fwdmatchcandidates::CPhiYMCH, // Phi - Y
fwdmatchcandidates::CPhiXMCH, // Phi - X
link
muonpropCov(1, 0), // Cov(Y, X), correct, equivalent to Cov(X, Y)
muonpropCov(2, 0), // Cov(Phi, X), should be Cov(Phi, Y) or muonpropCov(2, 1)
muonpropCov(2, 1), // Cov(Phi, Y), should be Cov(Phi, X) or muonpropCov(2, 0)
link

[github-actions]

O2 linter results: ❌ 30 errors, ⚠️ 11 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/o2 for 9e4e702 at 2026-04-21 17:02:

## sw/BUILD/O2Physics-latest/log
c++: fatal error: Killed signal terminated program cc1plus
ninja: build stopped: subcommand failed.

Full log here.