Update bytes conversion to 1e9 for GB

Just noticed on a 40GB job the returned bytes was 40,000,000, I think this is the correct conversion unless I have made an oversight.

slurmio/slurmio.py

@@ -166,6 +166,6 @@ def _trackable_resources(self) -> dict:
 
 def convert_mem_to_bytes(s):
     if s.endswith("G"):
-        return int(s[:-1]) * 10**6
+        return int(s[:-1]) * 10**9
     else:
         return int(s)