DOC: update env var description

Author: MarcBresson

doc/en/reference/reference.rst

@@ -2245,7 +2245,7 @@ All the command-line flags can be obtained by running ``pytest --help``::
                             Directory to take the pytester example files from
 
     Environment variables:
-      CI                       When truthy, pytest knows it is running in a CI process and does not truncate summary info
+      CI                       When set (regardless of value), pytest knows it is running in a CI process and does not truncate summary info
       BUILD_NUMBER             equivalent to CI
       PYTEST_ADDOPTS           Extra command line options
       PYTEST_PLUGINS           Comma-separated plugins to load during startup

src/_pytest/helpconfig.py

@@ -214,7 +214,7 @@ def showhelp(config: Config) -> None:
     vars = [
         (
             "CI",
-            "When truthy, pytest knows it is running in a CI process and does not truncate summary info",
+            "When set (regardless of value), pytest knows it is running in a CI process and does not truncate summary info",
         ),
         ("BUILD_NUMBER", "equivalent to CI"),
         ("PYTEST_ADDOPTS", "Extra command line options"),