Fix formatting in Kernel.md

Remove code formatting from headings for readability.

Author: Amanda Butler

docs/api/rtos/Kernel.md

@@ -6,7 +6,7 @@ The Kernel namespace implements interfaces to attach a function to some kernel e
 
 [![View code](https://www.mbed.com/embed/?type=library)](https://os.mbed.com/docs/development/mbed-os-api-doxy/namespacertos_1_1_kernel.html)
 
-### `get_ms_count()` example
+### get_ms_count() example
 
 The function `get_ms_count()` can be used to read the current RTOS kernel millisecond tick count. The below code snippet demonstrates use of the `get_ms_count()` function to calculate the elapsed time:
 
@@ -26,13 +26,13 @@ void send_data()
 
 ```
 
-### `attach_idle_hook()` example
+### attach_idle_hook() example
 
 The function `attach_idle_hook()` can be used to attach a function to be called by the RTOS idle task. The below code snippet demostrates the usage.
 
 [![View Example](https://www.mbed.com/embed/?url=https://github.com/ARMmbed/mbed-os-example-kernel-hooks)](https://github.com/ARMmbed/mbed-os-example-kernel-hooks/blob/master/main.cpp)
 
-### `attach_thread_terminate_hook()` example
+### attach_thread_terminate_hook() example
 
 The function `attach_thread_terminate_hook()` can be used to attach a function to be called when a thread terminates.