test: update getSassImplementation call sites to new 1-arg signature

The `loaderContext` parameter was removed from `getSassImplementation`
in 0f6dcd5 (it was unused). The implementation-option tests still
called it with the old `({}, undefined)` 2-arg form, which made `{}`
look like a valid implementation, hit the `else` branch of the
type-narrow, and threw "Unknown Sass implementation." before reaching
the actual assertion paths in:

- should try to load using valid order
- should not swallow an error when trying to load a sass implementation

Drop the no-op first argument so both tests exercise the intended
behavior again.

https://claude.ai/code/session_01UgvxAaf3W9xymtJRAyk7QB

Author: claude

package-lock.json

@@ -564,7 +564,7 @@ describe("implementation option", () => {
       const { getSassImplementation } = await import(
         `../src/utils.js?valid-order=${Date.now()}`
       );
-      const impl = await getSassImplementation({}, undefined);
+      const impl = await getSassImplementation(undefined);
 
       // sass-embedded is preferred when both load successfully.
       assert.match(impl.info, /^sass-embedded\t.*\[sass-embedded-mock\]/);
@@ -595,7 +595,7 @@ describe("implementation option", () => {
       );
 
       await assert.rejects(
-        getSassImplementation({}, undefined),
+        getSassImplementation(undefined),
         /Some error sass-embedded/,
       );
     } finally {