API Reference: __CPROVER_initialize is not part of the API

While it is a function that we generate and internally make heavy use
of, it isn't usable in source code (unlike all other functions
documented in the API Reference).

Author: tautschnig

doc/cprover-manual/api.md

@@ -47,16 +47,6 @@ relative to the base address of the object. The function
 **\_\_CPROVER\_DYNAMIC\_OBJECT** returns true if the pointer passed as
 arguments points to a dynamically allocated object.
 
-#### \_\_CPROVER\_initialize
-
-```C
-void __CPROVER_initialize(void);
-```
-
-The function **\_\_CPROVER\_initialize** computes the initial state of
-the program. It is called prior to calling the main procedure of the
-program.
-
 #### \_\_CPROVER\_input, \_\_CPROVER\_output
 
 ```C