Fix typos in Web Application Firewall Docs

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

doc/topics/web_application_firewall/index.md

@@ -55,7 +55,7 @@ you can configure a cluster on GKE. Once this is set up, you can follow the step
 
 NOTE: **Note**
 This guide shows how the WAF can be deployed using Auto DevOps. The WAF
-is avaliable by default to all applications no matter how they are deployed,
+is available by default to all applications no matter how they are deployed,
 as long as they are using Ingress.
 
 ## Network firewall vs. Web Application Firewall

doc/topics/web_application_firewall/quick_start_guide.md

@@ -12,7 +12,7 @@ need to ensure your own [Runners are configured](../../ci/runners/README.md) and
 [Google OAuth is enabled](../../integration/google.md).
 
 **Note**: GitLab's Web Application Firewall is deployed with [Ingress](../../user/clusters/applications.md#Ingress),
-so it will be avaliable to your applications no matter how you deploy them to Kubernetes.
+so it will be available to your applications no matter how you deploy them to Kubernetes.
 
 ## Enable or disable ModSecurity