package/python-urllib3: security bump to version 1.26.6

package/python-urllib3: security bump to version 1.26.6

Fix CVE-2021-33503: An issue was discovered in urllib3 before 1.26.5.
When provided with a URL containing many @ characters in the authority
component, the authority regular expression exhibits catastrophic
backtracking, causing a denial of service if a URL were passed as a
parameter or redirected to via an HTTP redirect.

https://github.com/urllib3/urllib3/blob/1.26.6/CHANGES.rst

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>