Update CI parallelization description

Signed-off-by: Rémy Coutable <remy@rymai.me>

doc/development/testing.md

@@ -493,24 +493,24 @@ Here are some things to keep in mind regarding test performance:
 
 Our current CI parallelization setup is as follows:
 
-1. The `knapsack` job in the prepare stage that is supposed to ensure we have a
-  `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file:
+1. The `retrieve-tests-metadata` job in the `prepare` stage ensures that we have
+  a `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file:
   - The `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file is fetched
     from S3, if it's not here we initialize the file with `{}`.
-1. Each `rspec x y` job are run with `knapsack rspec` and should have an evenly
-  distributed share of tests:
+1. Each `rspec-pg x y`/`rspec-mysql x y` job is run with `knapsack rspec` and
+  should have an evenly distributed share of tests:
   - It works because the jobs have access to the
     `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` since the "artifacts
     from all previous stages are passed by default". [^1]
-  - the jobs set their own report path to
+  - The jobs set their own report path to
     `KNAPSACK_REPORT_PATH=knapsack/${CI_PROJECT_NAME}/${JOB_NAME[0]}_node_${CI_NODE_INDEX}_${CI_NODE_TOTAL}_report.json`.
-  - if knapsack is doing its job, test files that are run should be listed under
+  - If knapsack is doing its job, test files that are run should be listed under
     `Report specs`, not under `Leftover specs`.
-1. The `update-knapsack` job takes all the
+1. The `update-tests-metadata` job takes all the
   `knapsack/${CI_PROJECT_NAME}/${JOB_NAME[0]}_node_${CI_NODE_INDEX}_${CI_NODE_TOTAL}_report.json`
-  files from the `rspec x y` jobs and merge them all together into a single
-  `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file that is then
-  uploaded to S3.
+  files from the `rspec-pg x y`/`rspec-mysql x y`jobs and merge them all together
+  into a single `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file that
+  is then uploaded to S3.
 
 After that, the next pipeline will use the up-to-date
 `knapsack/${CI_PROJECT_NAME}/rspec_report-master.json` file. The same strategy