Edit CI schedules doc according to Vale suggestions

doc/ci/pipelines/schedules.md

@@ -56,15 +56,15 @@ is installed on.
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/12328) in GitLab 9.4.
 
-You can pass any number of arbitrary variables and they will be available in
+You can pass any number of arbitrary variables. They are available in
 GitLab CI/CD so that they can be used in your [`.gitlab-ci.yml` file](../../ci/yaml/README.md).
 
 ![Scheduled pipeline variables](img/pipeline_schedule_variables.png)
 
 ### Using only and except
 
-To configure that a job can be executed only when the pipeline has been
-scheduled (or the opposite), you can use
+To configure a job to be executed only when the pipeline has been
+scheduled (or the opposite), use
 [only and except](../yaml/README.md#onlyexcept-basic) configuration keywords.
 
 For example:
@@ -102,7 +102,7 @@ For GitLab.com, refer to the [dedicated settings page](../../user/gitlab_com/ind
 
 ## Working with scheduled pipelines
 
-Once configured, GitLab supports many functions for working with scheduled pipelines.
+After configuration, GitLab supports many functions for working with scheduled pipelines.
 
 ### Running manually
 
@@ -128,7 +128,7 @@ The next time a pipeline is scheduled, your credentials are used.
 
 ![Schedules list](img/pipeline_schedules_ownership.png)
 
-If the owner of a pipeline schedule does not have the ability to create
+If the owner of a pipeline schedule cannot create
 pipelines on the target branch, the schedule stops creating new
 pipelines.