Remove unused LockAssertion struct

doc/developer-notes.md

@@ -793,25 +793,6 @@ bool ChainstateManager::ProcessNewBlock(...)
 }
 ```
 
-- When Clang Thread Safety Analysis is unable to determine if a mutex is locked, use `LockAssertion` class instances:
-
-```C++
-// net_processing.h
-void RelayTransaction(...) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
-
-// net_processing.cpp
-void RelayTransaction(...)
-{
-    AssertLockHeld(::cs_main);
-
-    connman.ForEachNode([&txid, &wtxid](CNode* pnode) {
-        LockAssertion lock(::cs_main);
-        ...
-    });
-}
-
-```
-
 - Build and run tests with `-DDEBUG_LOCKORDER` to verify that no potential
   deadlocks are introduced. As of 0.12, this is defined by default when
   configuring with `--enable-debug`.