Remove i686-apple-darwin cross-testing

Author: calebzulawski

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

@@ -49,9 +49,9 @@ const MIR_OPT_BLESS_TARGET_MAPPING: &[(&str, &str)] = &[
     ("i686-unknown-linux-musl", "x86_64-unknown-linux-musl"),
     ("i686-pc-windows-msvc", "x86_64-pc-windows-msvc"),
     ("i686-pc-windows-gnu", "x86_64-pc-windows-gnu"),
-    ("i686-apple-darwin", "x86_64-apple-darwin"),
     // ARM Macs don't have a corresponding 32-bit target that they can (easily)
     // build for, so there is no entry for "aarch64-apple-darwin" here.
+    // Likewise, i686 for macOS is no longer possible to build.
 ];
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]