Show output of panic found when updating fourslash tests

Author: sheetalkamat

internal/fourslash/_scripts/updateFailing.mts

@@ -21,7 +21,7 @@ function main() {
     const panicRegex = /^panic/m;
     if (panicRegex.test(testOutput)) {
         fs.writeFileSync(failingTestsPath, oldFailingTests, "utf-8");
-        throw new Error("Unrecovered panic detected in tests");
+        throw new Error("Unrecovered panic detected in tests\n" + testOutput);
     }
     const failRegex = /--- FAIL: ([\S]+)/gm;
     const failingTests: string[] = [];