delete(C5): InMemoryStore and the Cache Primitives edge

The W3-parked InMemoryStore is superseded by Store.InMemory in
swift-time-to-live (6f9a9db) — a fresh typed implementation, not a move,
per the parked ruling that the `Any`-erasure is a defect to drop at the
fill rather than carry across. The ssf side is therefore a pure deletion.

Drops the sole consumer of Cache Primitives in this package, so the
package dependency, the `.cachePrimitives` accessor, and the target edge
go with it. `exports.swift` needed no change.

Census: 0 remaining `InMemoryStore` references across 19,225 source and
test files in the 8 documented workspace roots; 0 remaining
`Cache_Primitives` references in this package's Sources+Tests, with a
positive control firing 4 hits inside the deleted file at HEAD.

Gated on fresh compilation (not cache): ServerFoundation and
ServerFoundationEnvVars recompiled from source, 13/13 tests passed after
recompiling the test target, swift-linter clean (0 errors), and
`swift-format lint --strict` clean.

Author: coenttb

Package.swift

@@ -13,7 +13,6 @@ extension Target.Dependency {
 }
 
 extension Target.Dependency {
-    static var cachePrimitives: Self { .product(name: "Cache Primitives", package: "swift-cache-primitives") }
     static var urlRequestHandler: Self { .product(name: "URLRequestHandler", package: "swift-urlrequest-handler") }
     static var nioCore: Self { .product(name: "NIOCore", package: "swift-nio") }
     static var nioEmbedded: Self { .product(name: "NIOEmbedded", package: "swift-nio") }
@@ -49,7 +48,6 @@ let package = Package(
         .library(name: .serverEnvVars, targets: [.serverEnvVars])
     ],
     dependencies: [
-        .package(url: "https://github.com/swift-primitives/swift-cache-primitives.git", branch: "main"),
         .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"),
@@ -68,7 +66,6 @@ let package = Package(
         .target(
             name: .serverFoundation,
             dependencies: [
-                .cachePrimitives,
                 .clocksDependencies,
                 .throttlingDependencies,
                 .translatingDependencies,