Clarifying secure metric descriptions

ee/config/metrics/counts_28d/20210216180355_user_api_fuzzing_jobs.yml

 ---
 data_category: operational
 key_path: usage_activity_by_stage_monthly.secure.user_api_fuzzing_jobs
-description: Count of API Fuzzing jobs by job name
+description: Count of distinct users creating API Fuzzing jobs.
 product_section: sec
 product_stage: secure
 product_group: group::dynamic analysis

ee/config/metrics/counts_all/20210216182023_projects_with_repositories_enabled.yml

 ---
 data_category: optional
 key_path: usage_activity_by_stage.create.projects_with_repositories_enabled
-description: Count of projects that have a matching Git repository, result of a Git
-  push action
+description: Count of users creating projects that have a matching Git repository,
+  result of a Git push action.
 product_section: dev
 product_stage: create
 product_group: group::source code