Replace purrr::invoke

[andrewelamb]

Replace all instances of invoke:

Warning (test-api_tags_queries.R:92:3): query_tags_with_parent_tags
`invoke()` was deprecated in purrr 1.0.0.
i Please use `exec()` instead.
Backtrace:
    ▆
 1. └─iatlasGraphQLClient::query_tags_with_parent_tags(tag = "not_a_tag") at test-api_tags_queries.R:92:2
 2.   ├─iatlasGraphQLClient::create_result_from_cursor_paginated_api_query(...) at iatlasGraphQLClient/R/api_tags_queries.R:332:2
 3.   └─purrr::invoke(...) at iatlasGraphQLClient/R/api_functions.R:145:2