Pontoon: Update Bosnian (bs) localization of Firefox for Android

Co-authored-by: Nihad Suljić <nihad.suljic92@gmail.com>

mozilla-mobile/fenix/app/src/main/res/values-bs/strings.xml

@@ -536,6 +536,8 @@
     <string name="onboarding_add_on_icon_content_description">Ikona dodatka</string>
     <!-- Content description for the an installed add-on icon. -->
     <string name="onboarding_installed_add_on_icon_content_description">Ikona instaliranog dodatka</string>
+    <!-- Content description for the an installing add-on icon. -->
+    <string name="onboarding_installing_add_on_icon_content_description">Instaliram ikonu dodatka</string>
     <!-- Content description for the add add-on button. -->
     <string name="onboarding_add_on_add_button_content_description">Dugme za dodavanje dodataka</string>
     <!-- Content description for the star rating group. -->