bug: fix dead code in luxminer _get_mac and _get_hashrate

Remove erroneous 'return None' statements placed outside except
blocks, making all subsequent logic unreachable. Same pattern was
already fixed for _get_wattage in 63bf0cd.

Author: wilfredallyn

pyasic/miners/backends/luxminer.py

@@ -233,7 +233,6 @@ async def _get_mac(self, rpc_config: dict | None = None) -> str | None:
                 rpc_config = await self.rpc.config()
             except APIError:
                 pass
-        return None
 
         if rpc_config is not None:
             try:
@@ -249,7 +248,6 @@ async def _get_hashrate(
                 rpc_summary = await self.rpc.summary()
             except APIError:
                 pass
-        return None
 
         if rpc_summary is not None:
             try: