Speed up tests locally by upto 45% (#1818)

# Which problem is this PR solving?
- This PR aims to add an additional flag to the jest script which would
make running tests locally even faster than ever.

## Description of the changes
- It uses `--maxWorkers=50%` flag to do so.

## How was this change tested?
- It was tested with several flags as below;

```bash
-----------------
yarn test

Time:        96.903 s
-----------------
yarn test --runInBand

Time:        131.721 s, estimated 606 s
-----------------
yarn test --maxWorkers=50%

Time:        53.295 s
-----------------
```

Operating System Used to Benchmark:
`Ubuntu 22`

## Checklist
- [x] I have read
https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
- [x] I have signed all commits
- [x] I have added unit tests for the new functionality
- [x] I have run lint and test steps successfully
  - for `jaeger`: `make lint test`
  - for `jaeger-ui`: `yarn lint` and `yarn test`

Signed-off-by: Ansh Goyal <anshgoyal1704@gmail.com>

packages/jaeger-ui/package.json

@@ -104,7 +104,7 @@
     "coverage": "yarn run test-ci --coverage",
     "start:ga-debug": "REACT_APP_GA_DEBUG=1 REACT_APP_VSN_STATE=$(../../scripts/get-tracking-version.js) vite",
     "start": "vite",
-    "test": "jest",
+    "test": "jest --maxWorkers=50%",
     "test-ci": "CI=1 jest --silent --color --maxWorkers=4"
   },
   "jest": {