update jest (#342)

Author: tsuyukimakoto

package.json

@@ -29,7 +29,7 @@
     "@types/jest": "26.0.15",
     "cpx": "1.5.0",
     "gas-webpack-plugin": "1.2.1",
-    "jest": "26.5.3",
+    "jest": "26.6.1",
     "prettier": "2.2.0",
     "rimraf": "3.0.2",
     "ts-jest": "26.4.4",