Generic/OpeningFunctionBraceBsdAllman: improve XML doc

- `<documentation>` title matches the sniff name.
- Mention in the `<standard>` description that there must be no content
on the line after the opening brace and makes some other minor
adjustments to the description text.
- Improve the title of the `<code>` blocks.

Author: rodrigoprimo

src/Standards/Generic/Docs/Functions/OpeningFunctionBraceBsdAllmanStandard.xml

@@ -1,19 +1,21 @@
-<documentation title="Opening Brace in Function Declarations">
+<documentation title="Opening Function Brace Bsd Allman">
     <standard>
     <![CDATA[
-    Function declarations follow the "BSD/Allman style". The function brace is on the line following the function declaration and is indented to the same column as the start of the function declaration.
+    Function declarations must follow the "BSD/Allman style". The opening brace is on the line
+    following the function declaration and is indented to the same column as the start of the
+    function declaration. The brace must be the last content on the line.
     ]]>
     </standard>
     <code_comparison>
-        <code title="Valid: Brace on next line.">
+        <code title="Valid: Opening brace on the next line.">
         <![CDATA[
 function fooFunction($arg1, $arg2 = '')
 <em>{</em>
     // Do something
 }
         ]]>
         </code>
-        <code title="Invalid: Brace on same line.">
+        <code title="Invalid: Opening brace on the same line.">
         <![CDATA[
 function fooFunction($arg1, $arg2 = '') <em>{</em>
     // Do something