sidebar: Use "decline" instead of "reject"

We already changed it in the Invite view, but not in the context menu.

src/session/view/sidebar/mod.ui

@@ -34,8 +34,8 @@
         <attribute name="hidden-when">action-missing</attribute>
       </item>
       <item>
-        <attribute name="label" translatable="yes">_Reject</attribute>
-        <attribute name="action">room-row.reject-invite</attribute>
+        <attribute name="label" translatable="yes">Dec_line</attribute>
+        <attribute name="action">room-row.decline-invite</attribute>
         <attribute name="hidden-when">action-missing</attribute>
       </item>
     </section>

src/session/view/sidebar/row.rs

@@ -330,7 +330,7 @@ mod imp {
                                 }
                             ))
                             .build(),
-                        gio::ActionEntry::builder("reject-invite")
+                        gio::ActionEntry::builder("decline-invite")
                             .activate(clone!(
                                 #[weak]
                                 obj,