Update histograms.xml comments

Remove pretty-print and validate format comments in all xmls under
histograms_xml/. Update their comments as well.

Change-Id: Ifd3ceddb3e649bb3c28ffe6d8dc32b8a979a8b2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2376670
Auto-Submit: Weilun Shi <sweilun@chromium.org>
Commit-Queue: Steven Holte <holte@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801845}

tools/metrics/histograms/histograms_xml/Fingerprint/histograms.xml

@@ -5,7 +5,7 @@ found in the LICENSE file.
 -->
 
 <!--
-This file is used to generate a comprehensive list of Chrome histograms along
+This file is used to generate a comprehensive list of Fingerprint histograms along
 with a detailed description for each histogram.
 
 For best practices on writing histogram descriptions, see
@@ -14,10 +14,6 @@ https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histogra
 For brief details on how to modify this file to add your description, see
 https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/one-pager.md
 
-Please pretty-print and validate your edits by running the pretty_print.py
-and validate_format.py scripts in the same directory as this file before
-uploading your change for review.
-
 Please send CLs to chromium-metrics-reviews@google.com rather than to specific
 individuals. These CLs will be automatically reassigned to a reviewer within
 about 5 minutes. This approach helps the metrics team to load-balance incoming

tools/metrics/histograms/histograms_xml/UMA/histograms.xml

@@ -5,7 +5,7 @@ found in the LICENSE file.
 -->
 
 <!--
-This file is used to generate a comprehensive list of Chrome histograms along
+This file is used to generate a comprehensive list of UMA histograms along
 with a detailed description for each histogram.
 
 For best practices on writing histogram descriptions, see
@@ -14,10 +14,6 @@ https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histogra
 For brief details on how to modify this file to add your description, see
 https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/one-pager.md
 
-Please pretty-print and validate your edits by running the pretty_print.py
-and validate_format.py scripts in the same directory as this file before
-uploading your change for review.
-
 Please send CLs to chromium-metrics-reviews@google.com rather than to specific
 individuals. These CLs will be automatically reassigned to a reviewer within
 about 5 minutes. This approach helps the metrics team to load-balance incoming

tools/metrics/histograms/histograms_xml/obsolete_histograms.xml

@@ -5,8 +5,8 @@ found in the LICENSE file.
 -->
 
 <!--
-This file is used to generate a comprehensive list of Chrome histograms along
-with a detailed description for each histogram.
+This file is used to store a list of obsolete Chrome histograms along with a detailed
+description for each histogram.
 
 For best practices on writing histogram descriptions, see
 https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/README.md
@@ -14,10 +14,6 @@ https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histogra
 For brief details on how to modify this file to add your description, see
 https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/one-pager.md
 
-Please pretty-print and validate your edits by running the pretty_print.py
-and validate_format.py scripts in the same directory as this file before
-uploading your change for review.
-
 Please send CLs to chromium-metrics-reviews@google.com rather than to specific
 individuals. These CLs will be automatically reassigned to a reviewer within
 about 5 minutes. This approach helps the metrics team to load-balance incoming