uniq: fix flaky test gnu_tests

The testcase tries to write to the stdin pipe while the process under
test is simultaneously exiting with an error code. Naturally, this is a
race, and we should ignore any stdin write errors. However, adding this
feature to the list makes it even more unreadable, and adds no real
value, so let's skip the input data entirely.

tests/by-util/test_uniq.rs

@@ -755,7 +755,7 @@ fn gnu_tests() {
         TestCase {
             name: "112",
             args: &["-D", "-c"],
-            input: "a a\na b\n",
+            input: "", // Note: Different from GNU test, but should not matter
             stdout: Some(""),
             stderr: Some("uniq: printing all duplicated lines and repeat counts is meaningless\nTry 'uniq --help' for more information.\n"),
             exit: Some(1),
@@ -811,7 +811,7 @@ fn gnu_tests() {
         TestCase {
             name: "119",
             args: &["--all-repeated=badoption"],
-            input: "a a\na b\n",
+            input: "", // Note: Different from GNU test, but should not matter
             stdout: Some(""),
             stderr: Some("uniq: invalid argument 'badoption' for '--all-repeated'\nValid arguments are:\n  - 'none'\n  - 'prepend'\n  - 'separate'\nTry 'uniq --help' for more information.\n"),
             exit: Some(1),