Update arguments.md

Removed obsolete `-promql.lookback-delta` option (deprecated since Cortex 1.2, replaced with `-querier.lookback-delta`). #3144 

Signed-off-by: Charlie Le <[email protected]>

Author: CharlieTLe

docs/configuration/arguments.md

@@ -53,7 +53,7 @@ The next three options only apply when the querier is used together with the Que
 
 ## Querier and Ruler
 
-- `-promql.lookback-delta`
+- `-querier.lookback-delta`
 
    Time since the last sample after which a time series is considered stale and ignored by expression evaluations.