(PDOC-233) Simplify logic for white space formatting of summary

Instead of specifying white space after each conditional, just add a
blank line at the end of the conditional similar to the `function.erb`
template.

lib/puppet-strings/markdown/templates/classes_and_defines.erb

@@ -2,14 +2,12 @@
 
 <% if text -%>
 <%= text %>
-
 <% elsif summary -%>
 <%= summary %>
-
 <% else -%>
 <%= "The #{name} class." %>
-
 <% end -%>
+
 <% if since -%>
 * **Since** <%= since %>
 

lib/puppet-strings/markdown/templates/resource_type.erb

@@ -2,14 +2,12 @@
 
 <% if text -%>
 <%= text %>
-
 <% elsif summary -%>
 <%= summary %>
-
 <% else -%>
 <%= "The #{name} type." %>
-
 <% end -%>
+
 <% if since -%>
 * **Since** <%= since %>