www/librespeed: update to 6.1.0

Changes: https://github.com/librespeed/speedtest/releases/tag/v6.0.0
Changes: https://github.com/librespeed/speedtest/releases/tag/v6.0.1
Changes: https://github.com/librespeed/speedtest/releases/tag/v6.0.2
Changes: https://github.com/librespeed/speedtest/releases/tag/v6.1.0