Rollup merge of #69349 - spastorino:mir-not-an-experiment, r=Dylan-DPC

MIR is not an experiment anymore

At least I hope is not :stuck_out_tongue_closed_eyes:

r? @oli-obk
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index 4f1b90e..284dd74 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -1,6 +1,6 @@
 /*!
 
-Rust MIR: a lowered representation of Rust. Also: an experiment!
+Rust MIR: a lowered representation of Rust.
 
 */