Update json-io version from 4.24.0 to 4.94.0

[jdereg]

Summary

Update the json-io library version reference in the README.md version table from 4.24.0 to 4.94.0 to reflect the current release.

• Updated json-io version in the library versions table from 4.24.0 → 4.94.0

[fabienrenaud]

Couple of notes:

• The version listed in the readme.md is meant to reflect the one used for the benchmarks reported on readme, so that's 4.24.0
• build.gradle uses version 4.88.0 (which you updated actually)
• Update AMI with newer JDK and EC2 instance type, README with new result graphs #126 will publish a new round of benchmark results soon (note: for v4.88.0)