Docs: Update path 'services' to 'partitions'

Due to the folder name is updated from 'secure_fw/services' to
'secure_fw/partitions', update related documents with updated name.

Change-Id: I5b85d3c2c4f2a4e1f7fd422910e968e970d70527
Signed-off-by: Ken Liu <ken.liu@arm.com>
diff --git a/docs/design_documents/tfm_its_service.rst b/docs/design_documents/tfm_its_service.rst
index 27f9300..c2315ea 100644
--- a/docs/design_documents/tfm_its_service.rst
+++ b/docs/design_documents/tfm_its_service.rst
@@ -70,7 +70,7 @@
 ``secure_fw/ns_callable/tfm_veneers.c`` - ITS veneers (auto-generated from
 manifest)
 
-``secure_fw/services/internal_trusted_storage/``
+``secure_fw/partitions/internal_trusted_storage/``
 
 - ``tfm_internal_trusted_storage.yaml`` - Partition manifest
 - ``tfm_its_secure_api.c`` - PSA ITS API implementation for SPE