Add diagram to ScopedRamExecutionLock.md

Add missing class hierarchy diagram for consistency.

Author: Amanda Butler

docs/api/platform/ScopedRamExecutionLock.md

@@ -1,5 +1,7 @@
 # ScopedRamExecutionLock
 
+<span class="images">![](https://os.mbed.com/docs/mbed-os/development/mbed-os-api-doxy/classmbed_1_1_scoped_ram_execution_lock.png)<span>ScopedRamExecutionLock class hierarchy</span></span>
+
 The `ScopedRamExecutionLock` class provides an RAII object for enabling execution from RAM. In other words, creating a ScopedRamExecutionLock object calls its constructor, which increments the RAM execution lock. The ScopedRamExecutionLock object automatically releases the RAM execution lock in its destructor when the object goes out of scope. Another way to look at this is when the ScopedRamExecutionLock object exists, it allows execution from RAM.
 
 ## ScopedRamExecutionLock class reference