[v6.38][main] rootbrowse: instance a TRint instead of TApplication

[silverweed]

BP of https://github.com/root-project/root/pull/20681

[github-actions[bot]]

Test Results

    21 files      21 suites   3d 16h 26m 11s ⏱️  3 707 tests  3 706 ✅ 0 💤 1 ❌ 75 982 runs  75 981 ✅ 0 💤 1 ❌

For more details on these failures, see this check.

Results for commit 0d5f382f.