Don't pass an unused --color to compiletest

This flag was an artifact of compiletest's old libtest-based test executor, and
currently doesn't influence compiletest's output at all.

Author: Zalathar

src/bootstrap/src/core/build_steps/test.rs

@@ -2401,7 +2401,6 @@ Please disable assertions with `rust.debug-assertions = false`.
         let git_config = builder.config.git_config();
         cmd.arg("--nightly-branch").arg(git_config.nightly_branch);
         cmd.arg("--git-merge-commit-email").arg(git_config.git_merge_commit_email);
-        cmd.force_coloring_in_ci();
 
         #[cfg(feature = "build-metrics")]
         builder.metrics.begin_test_suite(

src/tools/compiletest/src/lib.rs

@@ -136,8 +136,6 @@ fn parse_config(args: Vec<String>) -> Config {
         )
         .optflag("", "fail-fast", "stop as soon as possible after any test fails")
         .optopt("", "target", "the target to build for", "TARGET")
-        // FIXME: Should be removed once `bootstrap` will be updated to not use this option.
-        .optopt("", "color", "coloring: auto, always, never", "WHEN")
         .optopt("", "host", "the host to build for", "HOST")
         .optopt("", "cdb", "path to CDB to use for CDB debuginfo tests", "PATH")
         .optopt("", "gdb", "path to GDB to use for GDB debuginfo tests", "PATH")