revert CPAN change

Author: jacobcalvert

types-doc/cpan-definition.md

@@ -22,7 +22,7 @@ The structure of a PURL for this package type is:
 
 - **Requirement:** Required
 - **Native Label:** CPAN ID of the author/publisher
-- **Note:** `It MUST be written uppercase and is required`
+- **Note:** `It MUST be written uppercase and is required.`
 
 ## Name definition