build: Remove ipdb from test requirements (#3237)

[ipdb](https://pypi.org/project/ipdb) is not used by testing suite. To
avoid installing extra dependencies, remove it from requirements file.
Developers who find ipdb helpful can install the package themselves.

Author: rominf

requirements-testing.txt

@@ -10,5 +10,4 @@ executing
 asttokens
 responses
 pysocks
-ipdb
 setuptools