Merge pull request #7849 from TylerBloom/fix-client-delay-on-subscription-close

Fix client delay when subscription is terminated

Author: TylerBloom

.changeset/bright-needles-suffer.md

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+---
+"@apollo/server": patch
+---
+
+In the subscription callback server plugin, terminating a subscription now immediately closes the internal async generator. This avoids that generator existing after termination and until the next message is received.