Stop explicitly line-buffering standard output

This removes `stdbuf -oL`.

I had added the `stdbuf -oL` along with some other changes, but it
seems the most likely of any of them to be producing the numerous
new failures reporting "error while loading shared libraries: C:
cannot open shared object file" (treating `C:` as though it is
itself the name of a DLL to load) such as:

	    FAIL [   0.028s] gix-filter::filter pipeline::convert_to_git::only_driver_means_streaming_is_possible
    --- STDOUT:              gix-filter::filter pipeline::convert_to_git::only_driver_means_streaming_is_possible ---
    running 1 test
    test pipeline::convert_to_git::only_driver_means_streaming_is_possible ... FAILED
    failures:
    failures:
	pipeline::convert_to_git::only_driver_means_streaming_is_possible
    test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 47 filtered out; finished in 0.02s

    --- STDERR:              gix-filter::filter pipeline::convert_to_git::only_driver_means_streaming_is_possible ---
    failed to extract 'tests\fixtures\generated-archives\pipeline_repos.tar': Ignoring archive at 'tests\fixtures\generated-archives\pipeline_repos.tar' as GIX_TEST_IGNORE_ARCHIVES is set.
    thread 'pipeline::convert_to_git::only_driver_means_streaming_is_possible' panicked at tests\tools\src\lib.rs:567:17:
    fixture script of "bash" "D:\\a\\gitoxide\\gitoxide\\gix-filter\\tests\\fixtures\\pipeline_repos.sh" failed: stdout:
    stderr:       0 [main] bash 547 C:\Program Files\Git\usr\bin\bash.exe: *** fatal error - error while loading shared libraries: C: cannot open shared object file: No such file or directory
    note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

There were about 700 such failures, with a total of 719 failing
tests. Let's see if no longer running the `cargo nextest` command
through `stdbuf` makes them go away.

.github/workflows/ci.yml

@@ -97,8 +97,7 @@ jobs:
         env:
           GIX_TEST_IGNORE_ARCHIVES: 1
         run: |
-          stdbuf -oL -- cargo nextest --color=always run --workspace --no-fail-fast |&
-            tee nextest.log
+          cargo nextest --color=always run --workspace --no-fail-fast |& tee nextest.log
         continue-on-error: true
       - name: Check how many tests failed
         if: steps.nextest.outcome == 'failure'