doc: fix link for python2 get-pip.py

Script by the current link doesn't work with Python 2 anymore:
```
ERROR: This script does not work on Python 2.7 The minimum supported Python version is 3.6.
Please use https://bootstrap.pypa.io/2.7/get-pip.py instead.
```

Signed-off-by: Igor Ryzhov <iryzhov@nfware.com>

diff --git a/doc/developer/building-frr-for-ubuntu2004.rst b/doc/developer/building-frr-for-ubuntu2004.rst
index f7f8c63e5b8b00aae0b321adb66c3238352c5fc3..ef5d8da55116d4b85fc3b5dc37f4ff421f5b3f09 100644 (file)
--- a/doc/developer/building-frr-for-ubuntu2004.rst
+++ b/doc/developer/building-frr-for-ubuntu2004.rst
@@ -27,7 +27,7 @@ ubuntu apt repositories; in order to install it:
 
 .. code-block:: shell
 
-   curl https://bootstrap.pypa.io/get-pip.py --output get-pip.py
+   curl https://bootstrap.pypa.io/2.7/get-pip.py --output get-pip.py
    sudo python2 ./get-pip.py
 
    # And verify the installation