lib: ratelimit timestamps

Remove the timestamp passed for ratelimit checks. Let the limit
calculation obtain a timestamp when it needs it. Most transfers run
without active ratelimits and getting a fresh timestamp is unnecessary.

Closes #22292

tests/http/scorecard.py

@@ -71,6 +71,8 @@ class Card:
     def fmt_mbs(cls, val):
         if val is None or val < 0:
             return '--'
+        if val >= (1024 * 1024 * 1024):
+            return f'{val / (1024 * 1024 * 1024):.3g} GB/s'
         if val >= (1024 * 1024):
             return f'{val / (1024 * 1024):.3g} MB/s'
         if val >= 1024: