Drop canal network_plugin (#10100)

According to the canal github[1] the repo is not maintained over 5 years.
In addition, the README says
```
  Originally, we thought we might more deeply integrate the two projects
  (possibly even going as far as a rebranding!). However, over time it
  became clear that that wasn't really necessary to fulfil our goal of
  making them work well together. Ultimately, we decided to focus on
  adding features to both projects rather than doing work just to
  combine them.
```
So it is difficult to support canal by Kubespray at this situation.

[1]: https://github.com/projectcalico/canal

README.md

@@ -169,7 +169,6 @@ Note: Upstart/SysV init based OS types are not supported.
 - Network Plugin
   - [cni-plugins](https://github.com/containernetworking/plugins) v1.2.0
   - [calico](https://github.com/projectcalico/calico) v3.25.1
-  - [canal](https://github.com/projectcalico/canal) (given calico/flannel versions)
   - [cilium](https://github.com/cilium/cilium) v1.13.0
   - [flannel](https://github.com/flannel-io/flannel) v0.21.4
   - [kube-ovn](https://github.com/alauda/kube-ovn) v1.10.7
@@ -233,8 +232,6 @@ You can choose among ten network plugins. (default: `calico`, except Vagrant use
     and overlay networks, with or without BGP. Calico uses the same engine to enforce network policy for hosts,
     pods, and (if using Istio and Envoy) applications at the service mesh layer.
 
-- [canal](https://github.com/projectcalico/canal): a composition of calico and flannel plugins.
-
 - [cilium](http://docs.cilium.io/en/latest/): layer 3/4 networking (as well as layer 7 to protect and secure application protocols), supports dynamic insertion of BPF bytecode into the Linux kernel to implement security services, networking and visibility logic.
 
 - [weave](docs/weave.md): Weave is a lightweight container overlay network that doesn't require an external K/V database cluster.