Update URLs for new pypi! (#4194)

* Update URLs for new pypi!

* trailing slash

* grump
diff --git a/docs/development/custom-vectors/secp256k1.rst b/docs/development/custom-vectors/secp256k1.rst
index b19bf4e..e0579b4 100644
--- a/docs/development/custom-vectors/secp256k1.rst
+++ b/docs/development/custom-vectors/secp256k1.rst
@@ -29,4 +29,4 @@
 Download link: :download:`verify_secp256k1.py
 </development/custom-vectors/secp256k1/verify_secp256k1.py>`
 
-.. _`pure Python ecdsa`: https://pypi.python.org/pypi/ecdsa
+.. _`pure Python ecdsa`: https://pypi.org/project/ecdsa/
diff --git a/docs/development/getting-started.rst b/docs/development/getting-started.rst
index 415f5d8..96b4b6d 100644
--- a/docs/development/getting-started.rst
+++ b/docs/development/getting-started.rst
@@ -106,10 +106,10 @@
 .. _`Homebrew`: https://brew.sh
 .. _`MacPorts`: https://www.macports.org
 .. _`OpenSSL`: https://www.openssl.org
-.. _`pytest`: https://pypi.python.org/pypi/pytest
-.. _`tox`: https://pypi.python.org/pypi/tox
-.. _`virtualenv`: https://pypi.python.org/pypi/virtualenv
-.. _`pip`: https://pypi.python.org/pypi/pip
-.. _`sphinx`: https://pypi.python.org/pypi/Sphinx
+.. _`pytest`: https://pypi.org/project/pytest/
+.. _`tox`: https://pypi.org/project/tox/
+.. _`virtualenv`: https://pypi.org/project/virtualenv/
+.. _`pip`: https://pypi.org/project/pip/
+.. _`sphinx`: https://pypi.org/project/Sphinx/
 .. _`reStructured Text`: http://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html
 .. _`this Github issue`: https://github.com/rfk/pyenchant/issues/42