Fix list of LTS braches in CONTRIBUTING.md, and back link from BRANCHES.md

Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/BRANCHES.md b/BRANCHES.md
index a63f070..60218b0 100644
--- a/BRANCHES.md
+++ b/BRANCHES.md
@@ -62,7 +62,7 @@
 increase code size for a security fix.)
 
 For contributors, see the [Backwards Compatibility section of
-CONTRIBUTING](CONTRIBUTING.md#cackwords-compatibility).
+CONTRIBUTING](CONTRIBUTING.md#backwards-compatibility).
 
 ## Current Branches