Make download-xsd manpage punctuation consistent
Added some missing periods.
@@ -52,10 +52,10 @@ FLAGS
=====
`--no-download`
-: Do not download the XSD even if there is no artifact cached
+: Do not download the XSD even if there is no artifact cached.
`--force`
-: Continue even if a checksum on the cached file is incorrect
+: Continue even if a checksum on the cached file is incorrect.
`-h`, `--help`
: Prints help information.
