Install twine only when needed (#8099)

.ci/ubuntu_ci.sh

@@ -68,11 +68,6 @@ install_kivy_test_run_pip_deps() {
       --config "kivy:log_level:error"
   )
   python3 -m pip install -I "$CYTHON_INSTALL" coveralls
-  if [ $(python3 -c 'import sys; print("{}{}".format(*sys.version_info))') -le "35" ]; then
-    python3 -m pip install twine~=1.15.0
-  else
-    python3 -m pip install twine
-  fi
 }
 
 install_kivy_test_wheel_run_pip_deps() {

.ci/windows_ci.ps1

@@ -72,7 +72,6 @@ function Install-kivy-test-run-win-deps {
 
 function Install-kivy-test-run-pip-deps {
     python -m pip install pip wheel setuptools --upgrade
-    python -m pip install twine
 }
 
 function Install-kivy {