Docs: Fix bmqa_mocksession doxygen failure

The `bqma_mocksession` component does not generate docs due to a
Markdown syntax error:

```
/…/blazingmq/src/groups/bmq/bmqa/bmqa_mocksession.h:1520: warning: reached end of file while inside a '```' block! The command that should end the block seems to be missing!
```

The syntax error prevents any component-level documentation from being
generated for this file.  This patch fixes the syntax error, which
then allows the component-level documentation to be built.

Signed-off-by: Patrick M. Niedzielski <patrick@pniedzielski.net>

src/groups/bmq/bmqa/bmqa_mocksession.h

@@ -393,7 +393,7 @@
 ///       `emitting` on the @ref BMQA_EXPECT_CALL macro in synchronous mode is
 ///       meaningless.
 ///
-///```
+/// ```
 /// void unitTest()
 /// {
 ///     // MockSession created without an eventHandler.