Remove defunct -Z print-region-graph

Author: tmiasko

src/librustc_interface/tests.rs

@@ -500,7 +500,6 @@ fn test_debugging_options_tracking_hash() {
     untracked!(print_link_args, true);
     untracked!(print_llvm_passes, true);
     untracked!(print_mono_items, Some(String::from("abc")));
-    untracked!(print_region_graph, true);
     untracked!(print_type_sizes, true);
     untracked!(query_dep_graph, true);
     untracked!(query_stats, true);

src/librustc_session/options.rs

@@ -958,9 +958,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "print the LLVM optimization passes being run (default: no)"),
     print_mono_items: Option<String> = (None, parse_opt_string, [UNTRACKED],
         "print the result of the monomorphization collection pass"),
-    print_region_graph: bool = (false, parse_bool, [UNTRACKED],
-        "prints region inference graph. \
-        Use with RUST_REGION_GRAPH=help for more info (default: no)"),
     print_type_sizes: bool = (false, parse_bool, [UNTRACKED],
         "print layout information for each type encountered (default: no)"),
     profile: bool = (false, parse_bool, [TRACKED],