west: fix for Python prior to 3.10

"type | None" syntax is only available with Python from version 3.10,
fix building with earlier 3.x Python versions.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

scripts/west_commands/runners/core.py

@@ -777,7 +777,7 @@ def require(program: str, path: Optional[str] = None) -> str:
  raise MissingProgram(program)
  return ret
 
- def get_rtt_address(self) -> int | None:
+ def get_rtt_address(self) -> Optional[int]:
  '''Helper method for extracting a the RTT control block address.
 
  If args.rtt_address was supplied, returns that.