Rollup merge of rust-lang#53003 - GuillaumeGomez:stabilize-rustdoc-options, r=QuietMisdreavus

Stabilize --color and --error-format options in rustdoc

Fixes rust-lang#52980

cc @kennytm

r? @QuietMisdreavus

Author: kennytm

src/librustdoc/lib.rs

@@ -290,7 +290,7 @@ fn opts() -> Vec<RustcOptGroup> {
                      "edition to use when compiling rust code (default: 2015)",
                      "EDITION")
         }),
-        unstable("color", |o| {
+        stable("color", |o| {
             o.optopt("",
                      "color",
                      "Configure coloring of output:
@@ -299,7 +299,7 @@ fn opts() -> Vec<RustcOptGroup> {
                                           never  = never colorize output",
                      "auto|always|never")
         }),
-        unstable("error-format", |o| {
+        stable("error-format", |o| {
             o.optopt("",
                      "error-format",
                      "How errors and other messages are produced",