Remove unreachable "break" statements to silence harmless compiler warnings

from ICC.

FossilOrigin-Name: 0d7287e1bfdd5a392bf2fb17699e7cfd0b08bf61fab6cbf4b4bb347b3c4b4610

src/os_unix.c

@@ -7603,7 +7603,7 @@ static int proxyFileControl(sqlite3_file *id, int op, void *pArg){
       assert( 0 );  /* The call assures that only valid opcodes are sent */
     }
   }
-  /*NOTREACHED*/
+  /*NOTREACHED*/ assert(0);
   return SQLITE_ERROR;
 }