Fix the error message of the exception handle

[hellolittlej]

Context

• before the fix, the error returns

> {
>   "cause": null,
>   "stackTrace": [],
>   "message": "Recipient [Actor[akka://MantisMaster/user/$a#-1849032173]] had already been terminated. Message of type
>   [io.mantisrx.master.resourcecluster.ResourceClusterActor$GetAvailableTaskExecutorsRequest].",
>   "suppressed": [],
>   "localizedMessage": "Recipient [Actor[akka://MantisMaster/user/$a#-1849032173]] had already been terminated. Message of type
>   [io.mantisrx.master.resourcecluster.ResourceClusterActor$GetAvailableTaskExecutorsRequest]."
>   }

• however, it doesn't follow the same pattern as other endpoints which returns the error response, this will prevent our proxy to preserve the original error message and return to the clients.

• after the fix, the error returns

{
    "time": 1769415195068,
    "host": "MacBook-L6RQY",
    "error": "Recipient [Actor[akka://MantisMaster/user/$a#1399717107]] had already been terminated. Message of type [io.mantisrx.master.resourcecluster.ResourceClusterActor$GetAvailableTaskExecutorsRequest].",
    "requestId": -1
}

Checklist

• ./gradlew build compiles code correctly
• Added new tests where applicable
• ./gradlew test passes all tests
• Extended README or added javadocs where applicable

[github-actions]

Test Results

147 files   -  6  147 suites   - 6   8m 50s ⏱️ -35s
578 tests  - 86  570 ✅  - 82  7 💤  - 4  1 ❌ ±0 
578 runs   - 87  570 ✅  - 83  7 💤  - 4  1 ❌ ±0 

For more details on these failures, see this check.

Results for commit 4cf73d5. ± Comparison against base commit 0e7ae19.

This pull request removes 86 tests.

io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testCreateAddAndDeleteRules
io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testCreateScalerRuleFromEmpty
io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testCronTriggersSLAToKillOld
io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testDeleteScalerRule
io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testExpireOldJobs
io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testGetJobDetailsForArchivedJob
io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testGetLastSubmittedJob
io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testGetLastSubmittedJobSubject
io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testGetLastSubmittedJobSubjectWithWrongClusterNameFails
io.mantisrx.master.jobcluster.JobClusterAkkaTest ‑ testGetLastSubmittedJobWithCompletedOnly
…

♻️ This comment has been updated with latest results.