fix: Install terraform in Docker image to unblock deploy

[bryphe-coder]

Fixes #287 and re-enables our deploy at https://proto.cdr.dev

• Installs terraform in our images/coder/Dockerfile
• Re-enables our deploy GH action

Example of successful deploy run: https://github.com/coder/coder/runs/5241614008?check_suite_focus=true

TODO:

• Fix if: condition when deploy is green again

[codecov]

Codecov Report

Merging #319 (c0a8f8a) into main (e5db936) will increase coverage by 2.88%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #319      +/-   ##
==========================================
+ Coverage   64.81%   67.69%   +2.88%     
==========================================
  Files          67      138      +71     
  Lines         756     7256    +6500     
  Branches       74       74              
==========================================
+ Hits          490     4912    +4422     
- Misses        251     1841    +1590     
- Partials       15      503     +488     

Flag	Coverage Δ
unittest-go-macos-latest	66.44% <ø> (?)
unittest-go-ubuntu-latest	67.44% <ø> (?)
unittest-go-windows-latest	65.97% <ø> (?)
unittest-js	64.81% <ø> (ø)

Impacted Files	Coverage Δ
coderd/projectversion.go	55.22% <0.00%> (ø)
codersdk/provisioners.go	63.15% <0.00%> (ø)
pty/ptytest/ptytest.go	89.79% <0.00%> (ø)
database/postgres/postgres.go	70.73% <0.00%> (ø)
database/db.go	0.00% <0.00%> (ø)
provisioner/terraform/provision.go	71.62% <0.00%> (ø)
httpmw/projectversionparam.go	72.50% <0.00%> (ø)
codersdk/users.go	68.96% <0.00%> (ø)
coderd/parameter/compute.go	71.85% <0.00%> (ø)
httpmw/userparam.go	76.66% <0.00%> (ø)
... and 61 more

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