Do not use traits, since they are not supported by Xcode

This pull request fixes #1826, which broke `make test_GRDBDemo` with Xcode 26.0.1.

To reproduce the failure:

- Remove from ~/Library/Developer/Xcode/DerivedData all previous builds of GRDB and related stuff
- Run `make distclean test_GRDBDemo`

We expect a success, but it fails with error "Unable to find module dependency: 'GRDBSQLite'".

Author: groue

Package.swift

@@ -14,12 +14,6 @@ let darwinPlatforms: [Platform] = [
 ]
 var swiftSettings: [SwiftSetting] = [
     .define("SQLITE_ENABLE_FTS5"),
-    // Until Xcode has proper support for package traits, we must enable
-    // SQLITE_ENABLE_SNAPSHOT by default so that Xcode projects that build
-    // a Darwin app can depend on GRDB and profit from WAL snapshots.
-    // Package traits who want to disable snapshots must set SQLITE_DISABLE_SNAPSHOT.
-    // TODO: when Xcode support traits, remove all mentions of SQLITE_DISABLE_SNAPSHOT and update as below:
-    // .define("SQLITE_ENABLE_SNAPSHOT", .when(platforms: darwinPlatforms, traits: ["GRDBSQLite"])),
     .define("SQLITE_ENABLE_SNAPSHOT"),
 ]
 var cSettings: [CSetting] = []
@@ -56,10 +50,6 @@ let package = Package(
         .library(name: "GRDB", targets: ["GRDB"]),
         .library(name: "GRDB-dynamic", type: .dynamic, targets: ["GRDB"]),
     ],
-    traits: [
-        "GRDBSQLite",
-        .default(enabledTraits: ["GRDBSQLite"]),
-    ],
     dependencies: dependencies,
     targets: [
         .systemLibrary(
@@ -68,7 +58,7 @@ let package = Package(
         .target(
             name: "GRDB",
             dependencies: [
-                .target(name: "GRDBSQLite", condition: .when(traits: ["GRDBSQLite"])),
+                .target(name: "GRDBSQLite"),
             ],
             path: "GRDB",
             resources: [.copy("PrivacyInfo.xcprivacy")],