Fix wrong indents in tox.ini file

Always use four indents for clarity.

Those wrong indents have been added by !59 and !68.

See merge request it/cookiecutter-e3!69 of the template

Author: cookiecutter-e3

tox.ini

@@ -15,11 +15,11 @@ extras = test
 
 # Speed up coverage on Python >= 3.12
 setenv =
-  # Set COVERAGE_CORE only for Python >= 3.12
-  COVERAGE_CORE=sysmon
-  py311: COVERAGE_CORE=
-  py310: COVERAGE_CORE=
-  py39: COVERAGE_CORE=
+    # Set COVERAGE_CORE only for Python >= 3.12
+    COVERAGE_CORE=sysmon
+    py311: COVERAGE_CORE=
+    py310: COVERAGE_CORE=
+    py39: COVERAGE_CORE=
 
 # Run testsuite with coverage when '-cov' and with multi-threading when '-xdist'
 # is in the env name