Avoid calling resolve after reject

[fpoli]

The implementation of runTests returns a promise that, in case of failure, invokes both the resolve and reject callbacks. It looks like a bug and this PR fixes that.

vscode-test/lib/runTest.ts

Lines 182 to 189 in 8e8d7a8

	if (code === null) {
	reject(signal);
	} else if (code !== 0) {
	reject('Failed');
	}
	console.log('Done\n');
	resolve(code ?? -1);