Mention the correct job UUID env variable

Author: toolmantim

README.md

@@ -30,7 +30,7 @@ Example: `tmp/junit-*.xml`
 
 The regular expression (with capture group) that matches the job UUID in the junit file names. This is used to create the job links in the annotation.
 
-To use this, configure your test reporter to embed the `$BUILDKITE_JOB_UUID` environment variable into your junit file names. For example `"junit-buildkite-job-$BUILDKITE_JOB_UUID.xml"`.
+To use this, configure your test reporter to embed the `$BUILDKITE_JOB_ID` environment variable into your junit file names. For example `"junit-buildkite-job-$BUILDKITE_JOB_ID.xml"`.
 
 Default: `-(.*).xml`
 
@@ -52,4 +52,4 @@ rake
 
 ## License
 
-MIT (see [LICENSE](LICENSE))
+MIT (see [LICENSE](LICENSE))