Clarify tracer execution order

[eapache]

Since rmosolgo/graphql-ruby#3393 it should at
least be consistent.

[swalkinshaw]

graphql-metrics/lib/graphql/metrics/tracer.rb

Lines 107 to 111 in fe0ef76

	def capture_parsing_time
	# GraphQL::Query#result fires `parse` before the `execute_multiplex` event, so sometimes
	# `pre_context.multiplex_start_time_monotonic` isn't set.
	parsing_offset_time = pre_context.multiplex_start_time_monotonic || GraphQL::Metrics.current_time_monotonic
	timed_result = GraphQL::Metrics.time(parsing_offset_time) { yield }

This could be removed at some point if we required the new graphql version right?

[eapache]

🤔 yes, though the upstream PR isn't even in a cut version yet. File an issue on this repo to remind us?

[swalkinshaw]

Sure, done in #49