Doc: Removed TF-M prefix from document heading

This patch removes the TF-M/Trusted Firmware prefix from the
title heading across the documentation.

Change-Id: I60e0c6e48615f67ee040a0d6dbc7d6f1873856e7
Signed-off-by: Galanakis, Minos <minos.galanakis@arm.com>
diff --git a/docs/user_guides/tfm_user_guide.rst b/docs/user_guides/tfm_user_guide.rst
index f653e83..1c770e9 100644
--- a/docs/user_guides/tfm_user_guide.rst
+++ b/docs/user_guides/tfm_user_guide.rst
@@ -1,6 +1,6 @@
-#############################
-Trusted Firmware M user guide
-#############################
+##########
+User guide
+##########
 How to compile and run TF-M and example test application for CoreLink
 SSE-200 subsystem on the MPS2 board and on the Fast Model(FVP).