[LIVY-603][BUILD] Upgrade build spark version to 2.4.3
[LIVY-603][BUILD] Upgrade build spark version to 2.4.3

## What changes were proposed in this pull request?
Bump Spark 2.4 minor version to 2.4.3.

## How was this patch tested?
Existing test

Author: yihengwang <yihengwang@tencent.com>

Closes #179 from yiheng/bump_spark_2_4_3.

meisam/incubator-livy,meisam/incubator-livy,meisam/incubator-livy,ajbozarth/incubator-livy,meisam/incubator-livy,ajbozarth/incubator-livy,meisam/incubator-livy,ajbozarth/incubator-livy,ajbozarth/incubator-livy,ajbozarth/incubator-livy,ajbozarth/incubator-livy,meisam/incubator-livy