Hotfix: fix generic threat model file name

Fix the typo of generic threat model file name

Change-Id: I5b927f3a9aaefad279e70b6f6ed4b1cf6865a071
Signed-off-by: David Hu <david.hu@arm.com>
diff --git a/docs/threat_models/generic_thread_model.rst b/docs/threat_models/generic_threat_model.rst
similarity index 100%
rename from docs/threat_models/generic_thread_model.rst
rename to docs/threat_models/generic_threat_model.rst