Mark PWA link-capturing metrics as obsolete.

The code that records these was recently removed in
https://chromium-review.googlesource.com/c/chromium/src/+/1651529.

Bug: 975014
Change-Id: I5cd37662141c11f77e92018396d32502dddbb514
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1669091Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Commit-Queue: Raymes Khoury <raymes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671573}

tools/metrics/histograms/histograms.xml

@@ -37703,6 +37703,9 @@ uploading your change for review.
 
 <histogram name="Extensions.BookmarkApp.GetAppForCurrentURLDuration" units="ms"
     expires_after="M77">
+  <obsolete>
+    Removed 2019/05 as PWA link capturing has been removed.
+  </obsolete>
   <owner>mgiuca@chromium.org</owner>
   <owner>ortuno@chromium.org</owner>
   <summary>
@@ -37712,6 +37715,9 @@ uploading your change for review.
 
 <histogram name="Extensions.BookmarkApp.GetAppForWindowDuration" units="ms"
     expires_after="M77">
+  <obsolete>
+    Removed 2019/05 as PWA link capturing has been removed.
+  </obsolete>
   <owner>mgiuca@chromium.org</owner>
   <owner>ortuno@chromium.org</owner>
   <summary>
@@ -37722,6 +37728,9 @@ uploading your change for review.
 
 <histogram name="Extensions.BookmarkApp.GetTargetAppDuration" units="ms"
     expires_after="M77">
+  <obsolete>
+    Removed 2019/05 as PWA link capturing has been removed.
+  </obsolete>
   <owner>mgiuca@chromium.org</owner>
   <owner>ortuno@chromium.org</owner>
   <summary>
@@ -37757,6 +37766,9 @@ uploading your change for review.
 
 <histogram name="Extensions.BookmarkApp.NavigationResult"
     enum="BookmarkAppNavigationResult" expires_after="M77">
+  <obsolete>
+    Removed 2019/05 as PWA link capturing has been removed.
+  </obsolete>
   <owner>mgiuca@chromium.org</owner>
   <owner>ortuno@chromium.org</owner>
   <summary>
@@ -37767,6 +37779,9 @@ uploading your change for review.
 
 <histogram name="Extensions.BookmarkApp.TimeBetweenOpenAppAndLastNavigation"
     units="ms">
+  <obsolete>
+    Removed 2019/05 as PWA link capturing has been removed.
+  </obsolete>
   <owner>mgiuca@chromium.org</owner>
   <owner>ortuno@chromium.org</owner>
   <summary>