chore(ci): use parallelism of 8 instead of 7 for large jobs (#4544)

## Description
When we added testing for Python 3.11 we did not increase the CircleCI parallelism from 7 to 8.

This means we have some jobs which we expect get one node per-Python version which are now running 2 Python test suites on the same node.

## Reviewer Checklist
- [x] Title is accurate.
- [x] Description motivates each change.
- [x] No unnecessary changes were introduced in this PR.
- [x] Avoid breaking [API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces) changes unless absolutely necessary.
- [x] Tests provided or description of manual testing performed is included in the code or PR.
- [x] Release note has been added for fixes and features, or else `changelog/no-changelog` label added.
- [x] All relevant GitHub issues are correctly linked.
- [x] Backports are identified and tagged with Mergifyio.

.circleci/config.yml

@@ -360,7 +360,7 @@ jobs:
     resource_class: large
     docker:
       - image: *ddtrace_dev_image
-    parallelism: 7
+    parallelism: 8
     steps:
       - checkout
       - setup_riot
@@ -394,7 +394,7 @@ jobs:
 
   tracer:
     <<: *contrib_job
-    parallelism: 7
+    parallelism: 8
     steps:
       - run_test:
           pattern: "tracer"
@@ -420,7 +420,7 @@ jobs:
 
   opentracer:
     <<: *contrib_job
-    parallelism: 7
+    parallelism: 8
     steps:
       - run_tox_scenario:
           pattern: '^py.\+-opentracer'
@@ -736,7 +736,7 @@ jobs:
 
   flask:
     <<: *machine_executor
-    parallelism: 7
+    parallelism: 8
     steps:
       - run_test:
           # Run both flask and flask_cache test suites
@@ -748,7 +748,7 @@ jobs:
 
   gevent:
     <<: *contrib_job
-    parallelism: 7
+    parallelism: 8
     steps:
       - run_tox_scenario:
           pattern: '^gevent_contrib-'
@@ -769,7 +769,7 @@ jobs:
 
   grpc:
     <<: *machine_executor
-    parallelism: 7
+    parallelism: 8
     steps:
       - run_test:
           pattern: "grpc"
@@ -1085,7 +1085,7 @@ jobs:
 
   kombu:
     <<: *contrib_job
-    parallelism: 7
+    parallelism: 8
     docker:
       - image: *ddtrace_dev_image
       - image: *rabbitmq_image