[commit: ghc] ghc-8.6: Bump stm submodule (f458bca)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : ghc-8.6
Link       : http://ghc.haskell.org/trac/ghc/changeset/f458bca3a9667af95b8782747eab5b0e70cba4b4/ghc

>---------------------------------------------------------------

commit f458bca3a9667af95b8782747eab5b0e70cba4b4
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Sun Sep 16 16:51:53 2018 -0400

    Bump stm submodule


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f458bca3a9667af95b8782747eab5b0e70cba4b4
 libraries/stm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libraries/stm b/libraries/stm
index 4a1deb9..5f4d7c6 160000
--- a/libraries/stm
+++ b/libraries/stm
@@ -1 +1 @@
-Subproject commit 4a1deb98fc95e55d8a6762a7dfec1a7dfa8b49b2
+Subproject commit 5f4d7c6d07a760d935c9d96e62999f1ad38a5e43