Remove the default value of aqa-systemtestsRepo

[sophia-guo]

The default value of aqa-systemtestsRepo is set in aqa-tests/system/common.xml. It is unnecessary to reset it. That is we can deleted this line: https://github.com/adoptium/run-aqa/blob/master/action.yml#L26

With the default value of aqa-systemtestsRepo removed it would be better to call function getAqaSystemTestsRepo() only if aqa-systemtestsRepo is not empty and hence function getAqaSystemTestsRepo() do not need to care about the default value.

That is move the function call inside a if check block https://github.com/adoptium/run-aqa/blob/master/src/runaqa.ts#L63

 if (aqa-systemtestsRepo && aqa-systemtestsRepo.length !== 0) {
       getAqaSystemTestsRepo(aqasystemtestsRepo)
}

Hence

function getAqaSystemTestsRepo(aqasystemtestsRepo: string) {
  const repoBranch = parseRepoBranch(aqasystemtestsRepo)
  process.env.ADOPTOPENJDK_SYSTEMTEST_REPO = repoBranch[0];
  process.env.ADOPTOPENJDK_SYSTEMTEST_BRANCH = repoBranch[1];
}

[Aaradhyaa717]

Hi, I would like to work on this one.