Update tab_ui feature descriptions to be phone-only

Bug: 1057828
Change-Id: I5f2c3e6d24905471d268aec3119d86d1db26fdd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2095924Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750589}

chrome/browser/flag_descriptions.cc

@@ -1852,24 +1852,25 @@ const char kTabEngagementReportingDescription[] =
 
 const char kTabGridLayoutAndroidName[] = "Tab Grid Layout";
 const char kTabGridLayoutAndroidDescription[] =
-    "Allows users to see their tabs in a grid layout in the tab switcher.";
+    "Allows users to see their tabs in a grid layout in the tab switcher on "
+    "phones.";
 
 const char kTabGroupsAndroidName[] = "Tab Groups";
 const char kTabGroupsAndroidDescription[] =
-    "Allows users to create groups to better organize their tabs.";
+    "Allows users to create groups to better organize their tabs on phones.";
 
 const char kTabGroupsContinuationAndroidName[] = "Tab Groups Continuation";
 const char kTabGroupsContinuationAndroidDescription[] =
-    "Allows users to access continuation features in Tab Group.";
+    "Allows users to access continuation features in Tab Group on phones.";
 
 const char kTabGroupsUiImprovementsAndroidName[] = "Tab Groups UI Improvements";
 const char kTabGroupsUiImprovementsAndroidDescription[] =
-    "Allows users to access new features in Tab Group UI.";
+    "Allows users to access new features in Tab Group UI on phones.";
 
 const char kTabToGTSAnimationAndroidName[] = "Enable Tab-to-GTS Animation";
 const char kTabToGTSAnimationAndroidDescription[] =
     "Allows users to see an animation when entering or leaving the "
-    "Grid Tab Switcher.";
+    "Grid Tab Switcher on phones.";
 
 const char kTabGroupsName[] = "Tab Groups";
 const char kTabGroupsDescription[] =