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/platform/platform_introduction.rst b/docs/platform/platform_introduction.rst
index c49381f..3301415 100644
--- a/docs/platform/platform_introduction.rst
+++ b/docs/platform/platform_introduction.rst
@@ -62,9 +62,9 @@
         - `PSoc64.
           <https://www.cypress.com/documentation/product-brochures/cypress-psoc-64-secure-microcontrollers>`_
 
-    - Runtime Security Subsystem (RSS):
+    - Runtime Security Engine (RSE):
 
-        - :doc:`RSS. </platform/arm/rss/readme>`
+        - :doc:`RSE. </platform/arm/rss/readme>`
 
 The document :doc:`Platform Deprecation and Removal </integration_guide/platform/platform_deprecation>`
 lists the deprecated platforms, removed from the upstream.