Docs: Fix spelling typos

Signed-off-by: Antonio de Angelis <antonio.deangelis@arm.com>
Change-Id: Ie7729b848b7284696d9b546b676cb4f31ab5db47
diff --git a/docs/design_docs/software/code_sharing.rst b/docs/design_docs/software/code_sharing.rst
index 14db411..7d06eac 100644
--- a/docs/design_docs/software/code_sharing.rst
+++ b/docs/design_docs/software/code_sharing.rst
@@ -280,7 +280,7 @@
 
 
 *************************
-Useability considerations
+Usability considerations
 *************************
 Functions that only use local variables can be shared easily. However, functions
 that rely on global variables are a bit tricky. They can still be shared, but