docs: symbol-namespaces: fix reST warning with literal block

Use a literal block for the EXPORT_SYMBOL_GPL_FOR_MODULES() example to
avoid a Docutils warning about unmatched '*'. This ensures correct rendering
and keeps the source readable.

Warning:
Documentation/core-api/symbol-namespaces.rst:90: WARNING: Inline emphasis start-string without end-string. [docutils]

Signed-off-by: Khaled Elnaggar <[email protected]>
Reviewed-by: Bagas Sanjaya <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

Author: Khaled Elnaggar

Documentation/core-api/symbol-namespaces.rst

@@ -85,7 +85,7 @@ namespace cannot be imported.
 The macro takes a comma separated list of module names, allowing only those
 modules to access this symbol. Simple tail-globs are supported.
 
-For example:
+For example::
 
   EXPORT_SYMBOL_GPL_FOR_MODULES(preempt_notifier_inc, "kvm,kvm-*")