Docs: Rename RSS to RSE

Renames Runtime Security Subsytem (RSS) to Runtime Security Engine (RSE)
in the docs. This patch does not affect paths or code.

Signed-off-by: Jamie Fox <jamie.fox@arm.com>
Change-Id: Iecf170beef5ea694bd8eb682b877370a5eacda05
diff --git a/docs/contributing/maintainers.rst b/docs/contributing/maintainers.rst
index f5d25e7..dedfd08 100644
--- a/docs/contributing/maintainers.rst
+++ b/docs/contributing/maintainers.rst
@@ -137,7 +137,7 @@
     :email: `Emekcan.Aras@arm.com <emekcan.aras@arm.com>`__
     :github: `ememarar <https://github.com/ememarar>`__
 
-RSS
+RSE
 ^^^
 
 Jamie Fox