Rename noFrequencyBasedMinification to useFrequencyBasedMinification

This PR renames the parameternoFrequencyBasedMinification onJsCompilerConfig touseFrequencyBasedMinification, addressing the in-repo TODO inpackages/flutter_tools/lib/src/web/compiler_config.dart: "consider renaming this to be 'positive'. Double negatives are confusing." (TODO(kevmoo)).

What changes: The parameter is now positive:useFrequencyBasedMinification (defaulttrue). When set tofalse, the compiler still receives--no-frequency-based-minification. The CLI flag remains--no-frequency-based-minification; only the Dart API and internal naming change.

Why: Positive naming improves readability (e.g.useFrequencyBasedMinification: false is clearer thannoFrequencyBasedMinification: true). No behavior or CLI contract change.

Issues fixed: None. This addresses an in-repo TODO; an issue is not required for this trivial refactor per the template.

If you had to change anything in theflutter/tests repo, include a link to the migration guide as per thebreaking change policy.
N/A — no changes in flutter/tests.

Pre-launch Checklist

• I read theContributor Guide and followed the process outlined there for submitting PRs.
• I read theTree Hygiene wiki page, which explains my responsibilities.
• I read and followed theFlutter Style Guide, includingFeatures we expect every widget to implement.
• I signed theCLA.
• I listed at least one issue that this PR fixes in the description above. (N/A: trivial refactor; addresses in-repo TODO.)
• I updated/added relevant documentation (doc comments with///).
• I added new tests to check the change I am making, or this PR istest-exempt. (Existing tests updated; no new behavior.)
• I followed thebreaking change policy and addedData Driven Fixes where supported.
• All existing and new tests are passing.

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