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
 
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index b3a9547..dcaa360 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -52,8 +52,7 @@
 The list of maintained branches can be found in the [Current Branches section
 of BRANCHES.md](BRANCHES.md#current-branches).
 
-Currently maintained LTS branches are:
-1. [mbedtls-2.7](https://github.com/ARMmbed/mbedtls/tree/mbedtls-2.7)
+The only currently maintained LTS branch is:
 1. [mbedtls-2.16](https://github.com/ARMmbed/mbedtls/tree/mbedtls-2.16)