Revert naturalsize suffix ternary per review feedback

Restore if/elif/else suffix selection in naturalsize(); hugovk noted
ternaries do not automatically improve readability here.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: inquilabee

src/humanize/filesize.py

@@ -81,8 +81,12 @@ def naturalsize(
     Returns:
         str: Human readable representation of a filesize.
     """
-    suffix_key = "gnu" if gnu else "binary" if binary else "decimal"
-    suffix = suffixes[suffix_key]
+    if gnu:
+        suffix = suffixes["gnu"]
+    elif binary:
+        suffix = suffixes["binary"]
+    else:
+        suffix = suffixes["decimal"]
 
     base = 1024 if (gnu or binary) else 1000
     bytes_ = float(value)