Change IDS_PDF_PAGE_INDEX string to meet formatting rules

This change modifies IDS_PDF_PAGE_INDEX string to follow formatting
rules defined in: http://userguide.icu-project.org/formatparse/messages

Bug: 1043505
Change-Id: Iba763c3d6c7229603d8bea28d81ff2a91f473024
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2032690Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Kevin Babbitt <kbabbitt@microsoft.com>
Commit-Queue: Virender Singh <virens@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#737382}

components/pdf_strings.grdp

@@ -58,7 +58,7 @@
     <message name="IDS_PDF_PAGE_INDEX" desc="Accessible label for each page, describing the page number">
       {COUNT, plural,
          =1 {Page 1}
-         other {Page #}}
+         other {Page {COUNT}}}
     </message>
     <message name="IDS_PDF_DOCUMENT_PAGE_COUNT" desc="Accessible name of PDF document. It gives information about the number of pages in the PDF file">
       {COUNT, plural,