chore: remove fallback synthetic shadow import (BREAKING CHANGE) (#186)

packages/@lwc/jest-preset/src/setup.js

@@ -12,21 +12,7 @@ if (!nativeShadow) {
             '@lwc/synthetic-shadow is being loaded twice. Please examine your jest/jsdom configuration.'
         );
     }
-    try {
-        // Prior to @lwc/synthetic-shadow v2.45.3, calling `require('@lwc/synthetic-shadow')`
-        // is a no-op, and you have to directly require the file below.
-        // At some point (probably LWC v3.0.0), the below line should throw because the file does
-        // not exist anymore. See: https://github.com/salesforce/lwc/pull/3456
-        require('@lwc/synthetic-shadow/dist/synthetic-shadow.js');
-    } catch (err) {
-        // In newer versions of @lwc/synthetic-shadow, you can just do
-        // `require('@lwc/synthetic-shadow')` normally.
-        if (err && err.code === 'MODULE_NOT_FOUND') {
-            require('@lwc/synthetic-shadow');
-        } else {
-            throw err;
-        }
-    }
+    require('@lwc/synthetic-shadow/dist/synthetic-shadow.js');
 }
 
 // Provides temporary backward compatibility for wire-protocol reform: lwc > 1.5.0