Use /usr/bin/env python in partition_hashes

By using `/usr/bin/env python` we ensure that we'll be selecting the
correct Python version the user most likely expected to be used. The
most common usecase for this is when Reticulum is installed in a virtual
env.

partition_hashes

@@ -1,4 +1,4 @@
-#!/bin/python
+#!/usr/bin/env python
 
 # Copyright (C) 2023, Mark Qvist
 
@@ -32,4 +32,4 @@ calc_hash = hashlib.sha256(firmware_data[0:-32]).digest()
 part_hash = firmware_data[-32:]
 
 if calc_hash == part_hash:
-    print(RNS.hexrep(part_hash, delimit=False))
+    print(RNS.hexrep(part_hash, delimit=False))