Bump postgres-kit to 2.5.1 (#188)

postgres-kit has been updated to fix build conflicts with swift-nio

Author: noahpistilli

Package.swift

@@ -12,7 +12,7 @@ let package = Package(
     dependencies: [
         .package(url: "https://github.com/vapor/async-kit.git", from: "1.2.0"),
         .package(url: "https://github.com/vapor/fluent-kit.git", from: "1.0.0"),
-        .package(url: "https://github.com/vapor/postgres-kit.git", from: "2.3.0"),
+        .package(url: "https://github.com/vapor/postgres-kit.git", from: "2.5.1"),
     ],
     targets: [
         .target(name: "FluentPostgresDriver", dependencies: [