Remove the execute bit on AstDumpToNode.{h,cpp}

Accidentally set the +x bit on these two new files.  Thought I was
on my guard for this but still got it wrong.

Testing:  Not relevant
Reviewed: None




git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23591 3a8e244f-b0f2-452b-bcba-4c88e055c3ca