PromQL: Fix parser benchmark (#6495)
PromQL: Fix parser benchmark (#6495)

The parser benchmarks called the `ParseMetric` function instead of the `ParseExpr` function, which resulted in parsing failing every time.

This means only the case of PromQL parser failure was benchmarked.

Signed-off-by: Tobias Guggenmos <e4a4450e4651c64beb34964c0f3c164fefd114d7@redhat.com>
prometheus/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,kangwoo/prometheus,prometheus/prometheus,keegancsmith/prometheus,Gouthamve/prometheus,GoogleCloudPlatform/prometheus,kangwoo/prometheus,alileza/prometheus,keegancsmith/prometheus,alileza/prometheus,keegancsmith/prometheus,prometheus/prometheus,Gouthamve/prometheus,GoogleCloudPlatform/prometheus,Gouthamve/prometheus,Gouthamve/prometheus,alileza/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,kangwoo/prometheus,alileza/prometheus,prometheus/prometheus,kangwoo/prometheus,keegancsmith/prometheus