Remove registry lookup error test that only verified default throw propagation

The test stubbed getEnvironmentManager to throw and asserted the error
propagated through getEnvironmentManagerCapability, but the implementation
has no try/catch around that call. The test confirmed default JS/TS throw
semantics rather than any capability-specific behavior, and had no
equivalent counterpart for the package-manager registry lookup path.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: edvilme

src/test/extensionApi.capabilities.unit.test.ts

@@ -215,10 +215,4 @@ suite('PythonEnvironmentApiImpl - capability queries', () => {
         assert.ok(pkgProbe.notCalled);
         assert.ok(scopedProbe.notCalled);
     });
-
-    test('registry lookup errors reject', async () => {
-        const failure = new Error('registry lookup failed');
-        sinon.stub(managers, 'getEnvironmentManager').throws(failure);
-        await assert.rejects(api.getEnvironmentManagerCapability(ownerId, 'environments.list'), (e) => e === failure);
-    });
 });