Update exptected diagnostic text in `BuildPlanTests.testPkgConfigGenericDiagnostic`
Update exptected diagnostic text in `BuildPlanTests.testPkgConfigGenericDiagnostic`

apple/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager