stream-settings: Add info to can_remove_subscribers_group label.

Mention that admins can unsubscribe others from any channel
in the setting label.

tools/lib/capitalization.py

@@ -175,6 +175,8 @@ IGNORED_PHRASES = [
     r"hours",
     r"days",
     r"weeks",
+    # Used in "Who can unsubscribe others from this channel" label.
+    r"in addition to organization administrators",
 ]
 
 # Sort regexes in descending order of their lengths. As a result, the

web/templates/settings/group_setting_value_pill_input.hbs

@@ -1,5 +1,8 @@
 <div class="input-group">
-    <label class="group-setting-label">{{label}}</label>
+    <label class="group-setting-label">
+        {{label}}
+        {{#if label_parens_text}}(<i>{{label_parens_text}}</i>){{/if}}
+    </label>
     <div class="pill-container person_picker prop-element" id="{{#if prefix}}{{prefix}}{{else}}id_{{/if}}{{setting_name}}" data-setting-widget-type="group-setting-type">
         <div class="input" contenteditable="true" data-placeholder="{{t 'Add roles, groups or users' }}">
             {{~! Squash whitespace so that placeholder is displayed when empty. ~}}

web/templates/stream_settings/stream_types.hbs

@@ -69,6 +69,7 @@
         {{> ../settings/group_setting_value_pill_input
           setting_name="can_remove_subscribers_group"
           label=(t 'Who can unsubscribe others from this channel')
+          label_parens_text=(t 'in addition to organization administrators')
           prefix=prefix }}
 
         {{#if (or is_owner is_stream_edit)}}