stmhal/mpconfigport.h: Remove config of PY_THREAD_GIL to use default.

The default for the GIL is to enable it if threading is enabled, and this
is the recommended way to use threading with the stmhal port.

stmhal/mpconfigport.h

@@ -108,7 +108,6 @@
 #endif
 #define MICROPY_PY_UERRNO           (1)
 #define MICROPY_PY_THREAD           (0)
-#define MICROPY_PY_THREAD_GIL       (0)
 
 // extended modules
 #define MICROPY_PY_UCTYPES          (1)