Update old-style copyright headers

Updates old-style copyright headers to the new style, by removing "All
rights reserved." Also inserts "The" before "PDFium Authors", which is
required by both styles.

Mechanically generated by this command:
  PATTERN='Copyright \([0-9]\+\) \(The \)\?PDFium Authors. All rights reserved.'
  git grep -l "$PATTERN" \
  | xargs sed "s/$PATTERN/Copyright \1 The PDFium Authors/" -i''

Fixed: pdfium:1884
Change-Id: I6f781d811df8839e2e21b85f716529b813828bcd
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/100371
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: K. Moon <kmoon@chromium.org>
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index ea18500..bc0a914 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -494,11 +494,9 @@
 def ChecksCommon(input_api, output_api):
   results = []
 
-  # TODO(crbug.com/pdfium/1884): Fix existing breakage, then remove
-  # license_header='.*' to enable the license check.
   results.extend(
       input_api.canned_checks.PanProjectChecks(
-          input_api, output_api, license_header='.*', project_name='PDFium'))
+          input_api, output_api, project_name='PDFium'))
 
   return results