Prepare for merging from rust-lang/rust

This updates the rust-version file to e8f3cfc0de70bf82583591f6656e1fba3140253e.

src/tools/miri/rust-version

diff --git a/src/tools/miri/rust-version b/src/tools/miri/rust-version
index d32b6d0..f22aff7 100644
--- a/src/tools/miri/rust-version
+++ b/src/tools/miri/rust-version
@@ -1 +1 @@
-7fefa09b90ca57b8a0e0e4717d672d38a0ae58b5
+e8f3cfc0de70bf82583591f6656e1fba3140253e