Update tox configuration for version 4

Related to swh/meta#4959 (closed)

tox.ini

 [tox]
+requires =
+  tox>4
 envlist=black,flake8,mypy,py3-{core,db,server,github}
 
 [testenv]
@@ -24,7 +26,7 @@ commands =
 [testenv:py3]
 skip_install = true
 deps = tox
-commands = tox -e py3-core-db-server-github-slow-cover -- {posargs}
+commands = tox run -e py3-core-db-server-github-slow-cover -- {posargs}
 
 [testenv:black]
 skip_install = true
@@ -58,7 +60,7 @@ commands =
 # git HEAD of swh-docs, is executed on CI for each diff to prevent
 # breaking doc build
 [testenv:sphinx]
-whitelist_externals = make
+allowlist_externals = make
 usedevelop = true
 extras =
   testing-core
@@ -68,8 +70,7 @@ extras =
   github
 deps =
   # fetch and install swh-docs in develop mode
-  -e git+https://forge.softwareheritage.org/source/swh-docs#egg=swh.docs
-
+  -e git+https://gitlab.softwareheritage.org/swh/devel/swh-docs.git\#egg=swh.docs
 setenv =
   SWH_PACKAGE_DOC_TOX_BUILD = 1
   # turn warnings into errors
@@ -77,11 +78,10 @@ setenv =
 commands =
   make -I ../.tox/sphinx/src/swh-docs/swh/ -C docs
 
-
 # build documentation only inside swh-environment using local state
 # of swh-docs package
 [testenv:sphinx-dev]
-whitelist_externals = make
+allowlist_externals = make
 usedevelop = true
 extras =
   testing-core
@@ -92,7 +92,6 @@ extras =
 deps =
   # install swh-docs in develop mode
   -e ../swh-docs
-
 setenv =
   SWH_PACKAGE_DOC_TOX_BUILD = 1
   # turn warnings into errors