Removing Linux/amd64 specific subdependencies

[shlomi-noach]

Description

Reported by @systay, the merging of #7725 introduced a subdependency github.com/moby/term which does not build on MacOS:

> make build
Tue Apr 6 14:14:12 CEST 2021: Building source tree
# github.com/moby/term
../go/pkg/mod/github.com/moby/term@v0.0.0-20200429084858-129dac9f73f6/tc.go:13:28: undefined: unix.SYS_IOCTL
../go/pkg/mod/github.com/moby/term@v0.0.0-20200429084858-129dac9f73f6/tc.go:18:28: undefined: unix.SYS_IOCTL
../go/pkg/mod/github.com/moby/term@v0.0.0-20200429084858-129dac9f73f6/termios_bsd.go:24:31: undefined: unix.SYS_IOCTL
../go/pkg/mod/github.com/moby/term@v0.0.0-20200429084858-129dac9f73f6/termios_bsd.go:37:31: undefined: unix.SYS_IOCTL
make: *** [build] Error 2

This is a subdependency of github.com/fsouza/go-dockerclient, which is in itself a dependency of tengo.

We already user our own fork of tengo. I've submitted and merged planetscale/tengo#5, which removes any docker references, none of which we use. This removes the dependencies on aforementioned libraries. I tagged as v0.9.6-ps.v2

This PR instructs go.mod to use v0.9.6-ps.v2.

Checklist

• Should this PR be backported? (to v10)
• Tests were added or are not required
• Documentation was added or is not required

Impacted Areas in Vitess

Components that this PR will affect:

• Query Serving
• VReplication
• Cluster Management
• Build/CI
• VTAdmin

[deepthi]

@gedgar created #7787 yesterday to fix the same issue. However, I'm not sure if that will stick because the go mod tidy test is failing right now on it.

[shlomi-noach]

I ran go mod tidy and committed to #7787. If #7787 works, then I prefer that #7787 is merged over this PR, because this PR requires us to edit our fork of tengo and this causes maintainership pains.

[shlomi-noach]

closing since #7787 fixed the problem in a different way.

[shlomi-noach]

Again, dropped docker code from planetscale/tengo, and this removes dependency modules that are giving us some pains.