Remove unused rb_thread_create_mjit_thread

follow up https://github.com/ruby/ruby/pull/6006

1 files changed, 0 insertions, 2 deletions

diff --git a/mjit.c b/mjit.c
index 2e471146b8..c94a2cfc86 100644
--- a/mjit.c
+++ b/mjit.c
@@ -29,8 +29,6 @@
 
 #include "mjit_worker.c"
 
-extern int rb_thread_create_mjit_thread(void (*worker_func)(void));
-
 // Return an unique file name in /tmp with PREFIX and SUFFIX and
 // number ID.  Use getpid if ID == 0.  The return file name exists
 // until the next function call.