CI: update circleci API call (#10874)

Ref readthedocs/readthedocs-corporate#1680

Author: stsewd

.github/workflows/main.yml

@@ -23,7 +23,7 @@ jobs:
         --url https://circleci.com/api/v2/project/gh/readthedocs/readthedocs-corporate/pipeline \
         --user '${{ secrets.CIRCLECI_USER_TOKEN }}:' \
         --header 'content-type: application/json' \
-        --data '{"branch": "main", "parameters":{"CIRCLE_JOB": "tests"}}'
+        --data '{"branch": "main", "parameters":{"tests_only": true}}'
 
     - name: Trigger tests in readthedocs-ext
       run: |
@@ -32,4 +32,4 @@ jobs:
         --url https:/circleci.com/api/v2/project/gh/readthedocs/readthedocs-ext/pipeline \
         --user '${{ secrets.CIRCLECI_USER_TOKEN }}:' \
         --header 'content-type: application/json' \
-        --data '{"branch": "main", "parameters":{"CIRCLE_JOB": "tests"}}'
+        --data '{"branch": "main", "parameters":{"tests_only": true}}'