ci: Use general terms for CircleCI.

GitHub Actions supports doing more than just CI,
and so in some contexts it's less obvious that we're
talking about just the CI if we refer to it instead of CircleCI.

docs/_templates/layout.html

@@ -8,7 +8,7 @@
     {% if pagename in ["production/postgresql", "production/video-calls"] and release.endswith('+git') %}
     {#
     # This page doesn't exist in the stable documentation yet.
-    # This temporary workaround prevents CircleCI failure and should be removed after the next release.
+    # This temporary workaround prevents test failures and should be removed after the next release.
     #}
     <div class="admonition warning">
         <p class="first admonition-title">Warning</p>

docs/testing/linters.md

@@ -51,7 +51,7 @@ note are:
 * `--skip` and `--only`: Only run certain linters.
 * `-m`: Only check modified files.
 
-Finally, you can rely on our CircleCI setup to run linters for you,
+Finally, you can rely on our continuous integration setup to run linters for you,
 but it is good practice to run lint checks locally.
 
 ```eval_rst