Upgrade itertools crate from 0.11 to 0.12 version (#1214)

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

tests/integration/Cargo.toml

@@ -10,7 +10,7 @@ chrono = { version = "0.4", default-features = false }
 derive_more = "0.99"
 fnv = "1.0"
 futures = "0.3"
-itertools = "0.11"
+itertools = "0.12"
 juniper = { path = "../../juniper" }
 juniper_subscriptions = { path = "../../juniper_subscriptions" }
 serde = { version = "1.0", features = ["derive"] }