Revert "Have Glean stable views parse datetime metrics as timestamps (bug 1771733) (#3343)"

[sean-rose]

This reverts #3343, which had the unfortunate side effect of causing the search_derived.mobile_search_clients_daily_v1 ETL query to exceed the query complexity limit in the moz-fx-data-shared-prod project (bug 1803534).

We have requested that Google increase the query complexity limit in the moz-fx-data-shared-prod project, but that's not guaranteed to happen in a timely fashion (or at all), so in the meantime reverting #3343 is the easiest way to get the search_derived.mobile_search_clients_daily_v1 ETL (and all its downstream dependencies) working again.

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[fbertsch]

r+ assuming this is a straight revert