change 4 and 6 sentences correctly

resource/locales/en-US/admin/admin.json

@@ -3,7 +3,7 @@
     "management_wiki": "Management Wiki",
     "system_information": "System Information",
     "wiki_administrator": "Only Wiki administrator can access this page",
-    "assign_administrator": "You can assign administrator from Assign administrator button in the User management page",
+    "assign_administrator": "You can assign the selected user to be a wiki administrator on the User Management page using the 'Give Admin Access' button",
     "list_of_installed_plugins": "List of installed plugins",
     "package_name": "Package name",
     "specified_version": "Specified version",

resource/locales/en-US/welcome.md

@@ -25,5 +25,5 @@ Slack
 
 <a href="https://growi-slackin.weseek.co.jp/"><img src="https://growi-slackin.weseek.co.jp/badge.svg"></a>
 
-Please join Slack by all means to make GROWI better.
-In addition to discussing development, we also accept questions at the time of introduction.
+Let's join our Slack channel for all to help make GROWI better.
+In addition to discussing development, we also accept questions at the time of introduction.