fix(ci-visibility): remove extra requests performed if env var not set

[gnufede]

CI App: Remove extra requests performed if DD_CIVISIBILITY_ITR_ENABLED env var not set or False.

Checklist

• Change(s) are motivated and described in the PR description.
• Testing strategy is described if automated tests are not included in the PR.
• Risk is outlined (performance impact, potential for breakage, maintainability, etc).
• Change is maintainable (easy to change, telemetry, documentation).
• Library release note guidelines are followed.
• Documentation is included (in-code, generated user docs, public corp docs).
• OPTIONAL: PR description includes explicit acknowledgement of the performance implications of the change as reported in the benchmarks PR comment.

Reviewer Checklist

• Title is accurate.
• No unnecessary changes are introduced.
• Description motivates each change.
• Avoids breaking API changes unless absolutely necessary.
• Testing strategy adequately addresses listed risk(s).
• Change is maintainable (easy to change, telemetry, documentation).
• Release note makes sense to a user of the library.
• Reviewer has explicitly acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment.

[pr-commenter]

Benchmarks

Comparing candidate commit c8b3438 in PR branch gnufede/fix-api-call-under-env-var with baseline commit 1937b15 in branch 1.x.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 93 cases.

scenario:flasksimple-tracer-and-profiler

• 🟥 execution_time [+0.445ms; +0.565ms] or [+7.245%; +9.204%]