delete: the dead swift-environment edge

The `.environment` accessor and the `swift-environment` package
dependency were declared but referenced by no target — only
`.environmentDependencies` is live, and `ServerFoundationEnvVars`
re-exports `Environment_Dependencies`, which carries its own edge. SwiftPM
had been warning `dependency 'swift-environment' is not used by any
target` on every build.

Pre-existing rather than orphaned by the InMemoryStore deletion: at
bf7b9f0, before that change, the accessor was already declared and unused.
Kept out of 4c7bae7 for that reason and taken here on its own, but it is
the same dead-accessor-plus-dead-package-dependency shape as the Cache
Primitives edge removed there.

Gated: fresh compilation of both modules and the test target, 13/13 tests
passed, swift-linter 0 errors, `swift-format lint --strict` exit 0, and
the SwiftPM warning is gone from the build output.

Author: coenttb

Package.swift

@@ -23,7 +23,6 @@ extension Target.Dependency {
     static var throttlingDependencies: Self { .product(name: "Throttling Dependencies", package: "swift-throttling-dependencies") }
     static var translatingDependencies: Self { .product(name: "Translating Dependencies", package: "swift-translating-dependencies") }
     static var environmentDependencies: Self { .product(name: "Environment Dependencies", package: "swift-environment-dependencies") }
-    static var environment: Self { .product(name: "Environment", package: "swift-environment") }
     static var logging: Self { .product(name: "Logging", package: "swift-log") }
     static var throttling: Self { .product(name: "Throttling", package: "swift-throttling") }
     static var passwordValidation: Self { .product(name: "PasswordValidation", package: "swift-password") }
@@ -48,7 +47,6 @@ let package = Package(
         .library(name: .serverEnvVars, targets: [.serverEnvVars])
     ],
     dependencies: [
-        .package(url: "https://github.com/swift-foundations/swift-environment.git", branch: "main"),
         .package(url: "https://github.com/swift-foundations/swift-json-web-token.git", branch: "main"),
         .package(url: "https://github.com/swift-foundations/swift-password.git", branch: "main"),
         .package(url: "https://github.com/swift-foundations/swift-throttling.git", branch: "main"),