Update doc/api/deprecations.md

Co-Authored-By: Rich Trott <rtrott@gmail.com>

Author: trivikr

doc/api/deprecations.md

@@ -5,7 +5,7 @@
 
 Node.js may deprecate APIs for any of the following reasons:
 
-* Use of the API is considered to be unsafe
+* Use of the API is considered to be unsafe.
 * An improved alternative API is available
 * Breaking changes to the API are expected in a future major release.