[io] reduce compression buffer length

[ferdymercury]

This Pull request:

Changes or fixes:

Explore suggestions proposed in https://github.com/root-project/root/issues/14651

However: Not sure what to change though in line if (nout == 0 || nout >= fObjlen) { //this happens when the buffer cannot be compressed

Checklist:

• [ ] tested changes locally
• [ ] updated the docs (if necessary)

This PR fixes #

[github-actions[bot]]

Test Results

    20 files      20 suites   4d 6h 37m 29s ⏱️  3 663 tests  3 660 ✅ 0 💤 3 ❌ 71 547 runs  71 539 ✅ 5 💤 3 ❌

For more details on these failures, see this check.

Results for commit 09c64d8a.

:recycle: This comment has been updated with latest results.