[SPARK-22093][TESTS] Fixes `assume` in `UtilsSuite` and `HiveDDLSuite`

## What changes were proposed in this pull request?

This PR proposes to remove `assume` in `Utils.resolveURIs` and replace `assume` to `assert` in `Utils.resolveURI` in the test cases in `UtilsSuite`.

It looks `Utils.resolveURIs` supports multiple but also single paths as input. So, it looks not meaningful to check if the input has `,`.

For the test for `Utils.resolveURI`, I replaced it to `assert` because it looks taking single path and in order to prevent future mistakes when adding more tests here.

For `assume` in `HiveDDLSuite`, it looks it should be `assert` to test at the last
## How was this patch tested?

Fixed unit tests.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #19332 from HyukjinKwon/SPARK-22093.