test: exclude fetch-wbw.ts from the code coverage collection

since fetchWbw() is an IIFE (Immediately Invoked Function Expression)
which makes it harder to test
while returning not so much value to the stability of the code

jest.config.js

@@ -4,7 +4,7 @@ module.exports = {
     "./(components|etc|lib|pages)/**/*.(ts|tsx|js|jsx)",
     "!./(components|etc|lib|pages)/**/__tests__/**/*.test.(ts|tsx|js|jsx)",
     "!./(components|etc|lib|pages)/**/__mocks__/**/*.(ts|tsx|js|jsx)",
-    "!./etc/fetchers/fetch-wbw.json",
+    "!./etc/fetchers/fetch-wbw.ts",
   ],
   coverageThreshold: {
     global: {