Cleanup tox.ini (#57)

* Update tox.ini

Remove some old pass_env vars and old isolated build flag

* Update tox.ini

{{ cookiecutter.package_name }}/tox.ini

@@ -4,7 +4,6 @@ envlist =
     py{38,39,310,311}-test
     py38-test-oldestdeps
     build_docs
-isolated_build = true
 
 [testenv]
 # tox environments are constructed with so-called 'factors' (or terms)
@@ -21,17 +20,19 @@ description =
 
 # Pass through the following environment variables which may be needed for the CI
 pass_env =
-    HOME
-    WINDIR
-    LC_ALL
-    LC_CTYPE
-    CC
+    # A variable to tell tests we are on a CI system
     CI
-    TRAVIS
+    # Custom compiler locations (such as ccache)
+    CC
+    # Location of locales (needed by sphinx on some systems)
+    LOCALE_ARCHIVE
+    # If the user has set a LC override we should follow it
+    # (note LANG is automatically passed through by tox)
+    LC_ALL
 
 # Suppress display of matplotlib plots generated during docs build
 set_env =
-    MPLBACKEND=agg
+    MPLBACKEND = agg
 
 # Run the tests in a temporary directory to make sure that we don't import
 # the package from the source tree