[ci visibility] Fix copy-paste error in teamcity env vars

[albertvaka]

What does this PR do?
Fixes a copy-paste error where the wrong env var was being used to compute the pipeline URL for TeamCity.

[ivoanjo]

👍 LGTM. Is this checked in system-tests or elsewhere? It looks like it'd be good to have test coverage for it :)

[ivoanjo]

P.s.: We're working on fixing the unrelated CI hiccup, we should have it back to green soon and then I'll merge in the PR :)

[albertvaka]

We have a separate repo (not linking it here because it is private) with tests that run against all tracers (since the behaviour should be the same for all). We don't have tests for TeamCity yet but I will add them today.

[codecov-commenter]

Codecov Report

Merging #2562 (195d336) into master (04fd1be) will decrease coverage by 0.01%.
The diff coverage is 97.14%.

@@            Coverage Diff             @@
##           master    #2562      +/-   ##
==========================================
- Coverage   98.03%   98.02%   -0.01%     
==========================================
  Files        1124     1124              
  Lines       60656    60683      +27     
  Branches     2767     2767              
==========================================
+ Hits        59463    59487      +24     
- Misses       1193     1196       +3     

Impacted Files	Coverage Δ
lib/datadog/ci/ext/environment.rb	98.41% <0.00%> (ø)
...iling_native_extension/native_extension_helpers.rb	96.73% <100.00%> (+0.53%)	⬆️
...filing/collectors/cpu_and_wall_time_worker_spec.rb	94.75% <100.00%> (+0.01%)	⬆️
...datadog/profiling/native_extension_helpers_spec.rb	97.69% <100.00%> (+0.27%)	⬆️
lib/datadog/core/diagnostics/environment_logger.rb	97.63% <0.00%> (-0.79%)	⬇️
spec/datadog/profiling/native_extension_spec.rb	98.11% <0.00%> (-0.63%)	⬇️
...dog/profiling/collectors/cpu_and_wall_time_spec.rb	97.48% <0.00%> (-0.42%)	⬇️
...ng/contrib/active_support/cache/instrumentation.rb	86.20% <0.00%> (-0.10%)	⬇️
...ec/datadog/tracing/contrib/sidekiq/patcher_spec.rb	100.00% <0.00%> (+4.00%)	⬆️

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[ivoanjo]

I've merged in the master branch to fix CI, making this good to go -- pressing the magic button now!