Point color-studio to a commit instead of a branch

Locking dependencies to commits makes updating them a bit more
burdensome, but at least it makes the update intentional and not
automatic and surprising.

This change was done to test Xcode's behavior in monitoring
`Modules/Package.swift` and updating `Modules/Package.resolved`.

See
#24518 (comment)

Author: mokagio

Modules/Package.resolved

@@ -56,7 +56,10 @@ let package = Package(
         // We can't use wordpress-rs branches nor commits here. Only tags work.
         .package(url: "https://github.com/Automattic/wordpress-rs", revision: "alpha-20250505"),
         .package(url: "https://github.com/wordpress-mobile/GutenbergKit", from: "0.2.0"),
-        .package(url: "https://github.com/Automattic/color-studio", branch: "trunk"),
+        .package(
+            url: "https://github.com/Automattic/color-studio",
+            revision: "bf141adc75e2769eb469a3e095bdc93dc30be8de"
+        ),
         .package(url: "https://github.com/wordpress-mobile/AztecEditor-iOS", from: "1.20.0"),
     ],
     targets: XcodeSupport.targets + [