[KYUUBI #1141] Remove redundant unit

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### _Why are the changes needed?_
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Remove redundant unit. `MB`

```
2021-09-23 08:41:08.889 INFO spark.SparkSQLEngine:
    Spark application name: kyuubi_USER_root_6f67c12c-f362-4a07-87d0-7aa7e5f43171
          application ID:  spark-461363e9cc934d1986f7ae4191dc0410
          application web UI: http://spark-740a727c11ce3da7-driver-svc.default.svc:44692
          master: k8s://https://10.10.9.35:6443
          version: 3.1.2
          driver: [cpu: 1, mem: 1G]
          executor: [cpu: 2, mem: 2G MB, maxNum: 18]
    Start time: Thu Sep 23 08:40:39 UTC 2021

    User: root (shared mode: USER)
    State: LATENT
```
### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [ ] Add screenshots for manual tests if appropriate

- [x] [Run test](https://kyuubi.readthedocs.io/en/latest/develop_tools/testing.html#running-tests) locally before make a pull request

Closes #1141 from timothy65535/remove.

Closes #1141

af1827e9 [timothy65535] Remove redundant unit

Authored-by: timothy65535 <timothy65535@163.com>
Signed-off-by: ulysses-you <ulyssesyou@apache.org>

externals/kyuubi-spark-sql-engine/src/main/scala/org/apache/kyuubi/engine/spark/events/EngineEvent.scala

@@ -82,7 +82,7 @@ case class EngineEvent(
        |          master: $master
        |          version: $sparkVersion
        |          driver: [cpu: $driverCores, mem: $driverMemory]
-       |          executor: [cpu: $executorCore, mem: $executorMemory MB, maxNum: $maxExecutors]
+       |          executor: [cpu: $executorCore, mem: $executorMemory, maxNum: $maxExecutors]
        |    Start time: ${new Date(startTime)}
        |    ${if (endTime != -1L) "End time: " + new Date(endTime) else ""}
        |    User: $owner (shared mode: $shareLevel)