fix: s/ftl.async_call.ms_to_complete/ftl.call.ms_to_complete

[deniseli]

whoops

Metric #1
Descriptor:
     -> Name: ftl.call.ms_to_complete
     -> Description: duration in ms to complete a verb call
     -> Unit: ms
     -> DataType: Histogram
     -> AggregationTemporality: Cumulative

HistogramDataPoints #0
Data point attributes:
     -> ftl.call.verb.ref: Str(echo.echo)
     -> ftl.module.name: Str(echo)
     -> ftl.status.succeeded: Bool(true)
StartTimestamp: 2024-08-06 21:59:38.317129 +0000 UTC
Timestamp: 2024-08-06 22:00:33.317447 +0000 UTC
Count: 1
Sum: 17.000000
Min: 17.000000
Max: 17.000000

Issue: #2194

[safeer]

😄