fix gfm doc typo about two spaces for next line transfer

doc/user/markdown.md

@@ -604,7 +604,7 @@ This line is separated from the one above by two newlines, so it will be a *sepa
 This line is also a separate paragraph, but...
 This line is only separated by a single newline, so it's a separate line in the *same paragraph*.
-This line is also a separate paragraph, and...
+This line is also a separate paragraph, and...  
 This line is on its own line, because the previous line ends with two
 spaces.
 ```
@@ -616,7 +616,7 @@ This line is separated from the one above by two newlines, so it will be a *sepa
 This line is also begins a separate paragraph, but...
 This line is only separated by a single newline, so it's a separate line in the *same paragraph*.
-This line is also a separate paragraph, and...
+This line is also a separate paragraph, and...  
 This line is on its own line, because the previous line ends with two
 spaces.