update tox.ini template

otc_metadata/templates/tox.ini.j2

@@ -31,7 +31,7 @@ commands =
 
 [testenv:docs-pdf]
 deps = -r{toxinidir}/doc/requirements.txt
-whitelist_externals =
+allowlist_externals =
   mkdir
 commands =
   mkdir -p doc/build/pdf
@@ -46,7 +46,7 @@ commands =
 # HTML version
 [testenv:{{ doc.type }}]
 deps = -r{toxinidir}/doc/requirements.txt
-whitelist_externals =
+allowlist_externals =
   cp
   mkdir
 commands =
@@ -65,7 +65,7 @@ commands =
 # Json version (for search)
 [testenv:json-{{ doc.type }}]
 deps = -r{toxinidir}/doc/requirements.txt
-whitelist_externals =
+allowlist_externals =
   cp
   mkdir
   find
@@ -88,7 +88,7 @@ commands =
 # PDF version
 [testenv:{{ doc.type }}-pdf-docs]
 deps = -r{toxinidir}/doc/requirements.txt
-whitelist_externals =
+allowlist_externals =
   rm
   mkdir
   make