message: doc: fix grammar in doc/files.md
diff: @@ -109,7 +109,7 @@ Subdirectory | File | Description
  ## Legacy subdirectories and files
  -These subdirectories and files are no longer used by the Peercoin:
  +These subdirectories and files are no longer used by Peercoin:
  Path | Description | Repository notes
  ---------------|-------------|-----------------
  