Combine code examples into a single <code_comparison> block

Doing this based on the PR review
(#159 (comment))
as the valid code examples are essentially the same.

This commit also changes the changes the type cast used in the second
example to make it more clear that this sniff is not only about `(int)`
type casts.

Author: rodrigoprimo

src/Standards/Generic/Docs/Formatting/SpaceBeforeCastStandard.xml

@@ -8,23 +8,13 @@
         <code title="Valid: Single space before a cast operator.">
         <![CDATA[
 $integer =<em> </em>(int) $string;
+$c = $a .<em> </em>(string) $b;
         ]]>
         </code>
-        <code title="Invalid: No space before a cast operator.">
+        <code title="Invalid: No space or multiple spaces before a cast operator.">
         <![CDATA[
 $integer =<em></em>(int) $string;
-        ]]>
-        </code>
-    </code_comparison>
-    <code_comparison>
-        <code title="Valid: Single space before a cast operator.">
-        <![CDATA[
-$c = $a +<em> </em>(int) $b;
-        ]]>
-        </code>
-        <code title="Invalid: Multiple spaces before a cast operator.">
-        <![CDATA[
-$c = $a +<em>   </em>(int) $b;
+$c = $a .<em>   </em>(string) $b;
         ]]>
         </code>
     </code_comparison>