fix: fix pip download links (#541)

Author: swarnava

README.md

@@ -34,15 +34,15 @@ This library supports the following Python implementations:
 
 ## Installation
 
-Install from PyPi using [pip](http://www.pip-installer.org/en/latest/), a
+Install from PyPi using [pip](https://pip.pypa.io/en/latest/), a
 package manager for Python.
 
     pip install twilio
 
 Don't have pip installed? Try installing it, by running this from the command
 line:
 
-    $ curl https://raw.github.com/pypa/pip/master/contrib/get-pip.py | python
+    $ curl https://bootstrap.pypa.io/get-pip.py | python
 
 Or, you can [download the source code
 (ZIP)](https://github.com/twilio/twilio-python/zipball/main "twilio-python