Drop misleading messages in StandaloneTests

Test `execute()` in StandaloneTests asserts matching of lines between
expected standard output and actual output lines.  It also passes the
same actual lines (but in a `String` form) as a message to method
assertLinesMatch, which takes three arguments.  Same situation for
standard error.

Drop this confusing argument from the two calls to assertLinesMatch and
let class `AssertLinesMatch` construct the error message for us.

(cherry picked from commit 7da21dd)

Author: rybak

Diff for: platform-tooling-support-tests/src/test/java/platform/tooling/support/tests/StandaloneTests.java

@@ -354,8 +354,8 @@ void execute() throws IOException {
 		var workspace = Request.WORKSPACE.resolve("standalone");
 		var expectedOutLines = Files.readAllLines(workspace.resolve("expected-out.txt"));
 		var expectedErrLines = Files.readAllLines(workspace.resolve("expected-err.txt"));
-		assertLinesMatch(expectedOutLines, result.getOutputLines("out"), result.getOutput("out"));
-		assertLinesMatch(expectedErrLines, result.getOutputLines("err"), result.getOutput("err"));
+		assertLinesMatch(expectedOutLines, result.getOutputLines("out"));
+		assertLinesMatch(expectedErrLines, result.getOutputLines("err"));
 
 		var jupiterVersion = Helper.version("junit-jupiter-engine");
 		var vintageVersion = Helper.version("junit-vintage-engine");