[GR-16686] Update the version of MRI Ruby used for benchmarks.

PullRequest: truffleruby/914

Author: nirvdrum

ci.jsonnet

@@ -102,7 +102,7 @@ local part_definitions = {
     mri: {
       "$.benchmark.server":: { options: ["--", "--no-core-load-path"] },
       downloads+: {
-        MRI_HOME: { name: "ruby", version: "2.3.3" },
+        MRI_HOME: { name: "ruby", version: "2.6.3" },
       },
 
       environment+: {

doc/contributor/updating-ruby.md

@@ -49,6 +49,7 @@ You'll usually get some conflicts to work out.
 * Update `doc/legal/legal.md`
 * Update `doc/contributor/stdlib.md`
 * Update method lists - see `spec/truffle/methods_spec.rb`
+* Update `ci.jsonnet` to use the corresponding MRI version for benchmarking
 
 ## Update libraries from third-party repos