Fix capitalization in several new sections of the Environments docs

doc/ci/environments/deployment_approvals.md

@@ -5,7 +5,7 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 description: Require approvals prior to deploying to a Protected Environment
 ---
 
-# Deployment Approvals **(PREMIUM)**
+# Deployment approvals **(PREMIUM)**
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/215888) in GitLab 14.7 with a flag named `deployment_approvals`. Disabled by default.
 

doc/ci/environments/protected_environments.md

@@ -248,9 +248,9 @@ NOTE:
 Configuration [with the UI](https://gitlab.com/gitlab-org/gitlab/-/issues/325249)
 is scheduled for a later release.
 
-## Deployment Approvals
+## Deployment approvals
 
-Protected Environments can also be used to require manual approvals before deployments. See [Deployment Approvals](deployment_approvals.md) for more information.
+Protected environments can also be used to require manual approvals before deployments. See [Deployment approvals](deployment_approvals.md) for more information.
 
 <!-- ## Troubleshooting