Update docs/modules/os/operating_systems/docs/onboarding/index.rst

Co-authored-by: Oliver Pajonk <oliver@pjnk.de>
Signed-off-by: Leonardo Rossetti <oss@lrossetti.com>

Author: odra

docs/modules/os/operating_systems/docs/onboarding/index.rst

@@ -88,7 +88,7 @@ Promotion to Certifiable
   and maintains them across all increments.
 
 **Eligibility requirements (Platform Maintainer / supplier requirements)**
-  The platform maintainer must fulfil the Certifiable level supplier requirements as defined in:
+  The platform maintainer must fulfill the Certifiable level supplier requirements as defined in:
   :ref:`platform_assumptions`.
 
 **Additional acceptance requirements (S-CORE / system integrator requirements)**