Fix misleading UNIMPLEMENTED in image load

This function works with VkFormat, not spv::ImageFormat (due to input
attachments)

Change-Id: I36a36a94127533a009df8f806b55ff2845162a76
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/35528
Tested-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
diff --git a/src/Pipeline/SpirvShader.cpp b/src/Pipeline/SpirvShader.cpp
index dc99bfa..45229cd 100644
--- a/src/Pipeline/SpirvShader.cpp
+++ b/src/Pipeline/SpirvShader.cpp
@@ -5634,7 +5634,7 @@
 			dst.move(3, SIMD::Float(1));
 			break;
 		default:
-			UNIMPLEMENTED("spv::ImageFormat %d", int(vkFormat));
+			UNIMPLEMENTED("VkFormat %d", int(vkFormat));
 			break;
 		}