west: runners: nrf: Fix typo in nrjfprog runner

The correct string is `ERASE_NONE`.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>

Author: carlescufi

scripts/west_commands/runners/nrfjprog.py

@@ -93,7 +93,7 @@ def do_exec_op(self, op, force=False):
                     cmd.append('--sectoranduicrerase')
                 else:
                     cmd.append('--sectorerase')
-            elif erase == 'NO_ERASE':
+            elif erase == 'ERASE_NONE':
                 pass
             else:
                 raise RuntimeError(f'Invalid erase mode: {erase}')