rename ambigous 'l' to 'df_fields' (ruff fix)

src/mpsd_hpc_tools/quota.py

@@ -86,10 +86,10 @@ def df_mountpoint(path: pathlib.Path) -> Tuple[int, int, int]:
     except:
         return None, None, None
     for line in output.splitlines():
-        l = line.split()
-        if (l[0] == "Filesystem"):
+        df_fields = line.split()
+        if (df_fields[0] == "Filesystem"):
             continue
-        (size, used, avail) = [int(li) for li in l[1:4]]
+        (size, used, avail) = [int(df_field) for df_field in df_fields[1:4]]
     return size, used, avail