test: increase test snapshot failure to 2%

It looks like GitHub Actions CI makes images which are up
to 1.6% different from the test snapshots from my PC,
however these images look pretty much exactly the same.

test/index.test.js

@@ -77,7 +77,7 @@ async function testScreenshotSnapshot(
     // if it's on a local PC, we can just open up the file
     dumpInlineDiffToConsole: process.env["CI"],
     comparisonMethod: "ssim",
-    failureThreshold: 0.01,
+    failureThreshold: 0.02,
     failureThresholdType: "percent",
   });
 }