fix: Remove build_code fallback for --name option

[sentry]

This change modifies the --name option in the codecov_cli/commands/upload.py command to remove FallbackFieldEnum.build_code from its fallback chain. Previously, if job_name was not available, --name would fall back to the build_code.

The original intent behind introducing job_name as a fallback (commit f7cb28c4) was to provide a more human-readable name for uploads, moving away from generic numeric build IDs. By removing build_code as a secondary fallback, the --name option will now only auto-populate if job_name is available (e.g., on GitHub Actions, where GITHUB_WORKFLOW and GITHUB_JOB are used). For other CI providers where _get_job_name is not implemented, --name will default to None if not explicitly provided by the user, aligning with the goal of either a meaningful name or no auto-population.

Fixes CLI-GE

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[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
723	1	722	1

View the full list of 1 ❄️ flaky test(s)

api.temp.calculator.test_calculator::test_divide

Flake rate in main: 100.00% (Passed 0 times, Failed 1726 times)

Stack Traces | 0.001s run time

def
                test_divide():
                > assert Calculator.divide(1, 2) == 0.5
                E assert 1.0 == 0.5
                E + where 1.0 = <function Calculator.divide at 0x104c9eb90>(1, 2)
                E + where <function Calculator.divide at 0x104c9eb90> = Calculator.divide
                .../temp/calculator/test_calculator.py:30: AssertionError

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