[enh] add missing text in square bracket

Some square brackets are empty, but they do have caption along with
them.  So I've put same text as caption in empty square brackets.

Author: Vipul Kumar

book/06-github/sections/4-managing-organization.asc

@@ -41,7 +41,7 @@ The Organization page shows you a simple dashboard of all the repositories, user
 
 [[_org_page]]
 .The Organization page
-image::images/orgs-01-page.png[]
+image::images/orgs-01-page.png[The Organization page]
 
 To manage your Teams, you can click on the Teams sidebar on the right hand side of the page in <<_org_page>>.
 This will bring you to a page you can use to add members to the team, add repositories to the team or manage the settings and access control levels for the team.
@@ -50,7 +50,7 @@ You can change that level by clicking the ``Settings'' button in <<_team_page>>.
 
 [[_team_page]]
 .The Team page
-image::images/orgs-02-teams.png[]
+image::images/orgs-02-teams.png[The Team page]
 
 When you invite someone to a team, they will get an email letting them know they've been invited.
 
@@ -67,6 +67,6 @@ You can go to the 'Audit Log' tab and see what events have happened at an organi
 
 [[_the_audit_log]]
 .The Audit log
-image::images/orgs-03-audit.png[]
+image::images/orgs-03-audit.png[The Audit log]
 
 You can also filter down to specific types of events, specific places or specific people.