Update dependency @apollo/client to v3.3.21

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@apollo/client (source)	3.3.20 -> 3.3.21

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Release Notes

apollographql/apollo-client

### [`v3.3.21`](https://togithub.com/apollographql/apollo-client/blob/master/CHANGELOG.md#Apollo-Client-3321) [Compare Source](https://togithub.com/apollographql/apollo-client/compare/v3.3.20...v3.3.21) ##### Bug fixes - Fix race condition in `@apollo/client/link/context` that could leak subscriptions if the subscription is cancelled before `operation.setContext` is called.
[@​sofianhn](https://togithub.com/sofianhn) in [#​8399](https://togithub.com/apollographql/apollo-client/pull/8399) - Prefer `existing.pageInfo.startCursor` and `endCursor` (if defined) in `read` function of `relayStylePagination` policies.
[@​benjamn](https://togithub.com/benjamn) in [#​8438](https://togithub.com/apollographql/apollo-client/pull/8438) ##### Improvements - Normalize user-provided `HttpLink` headers by lower-casing their names.
[@​benjamn](https://togithub.com/benjamn) in [#​8449](https://togithub.com/apollographql/apollo-client/pull/8449)

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