Fix typo in warning message for Path.Combine

Author: jonjanego

csharp/ql/src/Bad Practices/PathCombine.ql

@@ -16,4 +16,4 @@ import semmle.code.csharp.frameworks.System
 
 from MethodCall call
 where call.getTarget().hasFullyQualifiedName("System.IO", "Path", "Combine")
-select call, "Call to 'System.IO.Path.Combine' may silently drop its earlier arguments"
+select call, "Call to 'System.IO.Path.Combine' may silently drop its earlier arguments."