[Build] Remove orphan file (delta-io#2791)

#### Which Delta project/connector is this regarding?
- [ ] Spark
- [ ] Standalone
- [ ] Flink
- [ ] Kernel
- [X] Other (Build)

## Description
MiMaExcludes.scala theoretically has being renamed to
SparkMimaExcludes.scala:

https://github.com/delta-io/delta/pull/1952/files#diff-e7ee88f4ceae7019f7bff3eef41ee5cee6da1e54c436df887e3fd4c96c282eda

For some reason both files exist, the former not being used.

@allisonport-db 

## How was this patch tested?
Unit Tests

## Does this PR introduce _any_ user-facing changes?
No

Signed-off-by: Felipe Pessoto <[email protected]>

Author: felipepessoto