🚨 Fix linter warnings of type 'name[casing]'

ansible-lint reads like this:

    name[casing]: All names should start with an uppercase letter.

While at it: Some task/handler names were slightly adapted to better
match what should be done.

roles/apache_letsencrypt/handlers/main.yml

@@ -1,6 +1,6 @@
 # Handlers for role apache_letsencrypt
 ---
-- name: restart apache2
+- name: Restart apache2
   service:
     name: apache2
     state: restarted

roles/apache_letsencrypt/tasks/main.yml

@@ -7,7 +7,7 @@
     mode: "0644"
     owner: root
     group: root
-  notify: restart apache2
+  notify: Restart apache2
 
 - name: Add symlink to enable configuration
   ansible.builtin.file:
@@ -17,4 +17,4 @@
     mode: "0644"
     owner: root
     group: root
-  notify: restart apache2
+  notify: Restart apache2