Make check quieter and throw error on "note".

Less output means it is easier to see the check results. If packages fail to install I can re-enable the output for the duration of the investigation.

.gitlab-ci.yml

@@ -6,8 +6,8 @@
     - merge_requests
     - tags
   script:
-    - R -e 'devtools::install_deps()'
-    - R -e 'devtools::check(error_on = "warning")'
+    - R -e 'devtools::install_deps(quiet = TRUE)'
+    - R -e 'devtools::check(error_on = "note")'
 
 # latest version of the previous minor R release
 check-previous: