Bug 1532800 Clarify Run in Private Windows description r=flod,mstriemer

Differential Revision: https://phabricator.services.mozilla.com/D22570

--HG--
extra : moz-landing-system : lando

toolkit/locales/en-US/toolkit/about/aboutAddons.ftl

@@ -129,7 +129,7 @@ detail-update-manual =
 # Used as a description for the option to allow or block an add-on in private windows.
 detail-private-browsing-label = Run in Private Windows
 
-detail-private-browsing-description = Extension will work in Private Windows, and have access to your online activities. <label data-l10n-name="detail-private-browsing-learn-more">Learn more</label>
+detail-private-browsing-description2 = When allowed, the extension will have access to your online activities while private browsing. <label data-l10n-name="detail-private-browsing-learn-more">Learn more</label>
 
 detail-private-browsing-on =
     .label = Allow

toolkit/mozapps/extensions/content/extensions.xul

@@ -559,7 +559,7 @@
                             </hbox>
                           </row>
                           <hbox class="detail-row-footer" id="detail-privateBrowsing-row-footer">
-                            <description class="indent preferences-description" data-l10n-id="detail-private-browsing-description">
+                            <description class="indent preferences-description" data-l10n-id="detail-private-browsing-description2">
                               <label id="detail-private-browsing-learnmore-link" class="learnMore" data-l10n-name="detail-private-browsing-learn-more" is="text-link"/>
                             </description>
                           </hbox>