[flang] Remove #includes that were used for debugging.

Original-commit: flang-compiler/f18@828ee8c2f0
Reviewed-on: https://github.com/flang-compiler/f18/pull/9
Tree-same-pre-rewrite: false

flang/lib/parser/provenance.h

@@ -5,7 +5,6 @@
 #include "source.h"
 #include <map>
 #include <memory>
-#include <ostream>
 #include <sstream>
 #include <string>
 #include <utility>

flang/lib/parser/source.cc

@@ -5,7 +5,6 @@
 #include <cerrno>
 #include <cstring>
 #include <fcntl.h>
-#include <iostream>  // TODO pmk rm
 #include <memory>
 #include <sys/mman.h>
 #include <sys/stat.h>