Standardize capability heading in practice files

[npatterson]

Matching the new-practices.md template, Practice files should use Supported Capabilities as the section heading, but 20 files use inconsistent headings:

• 19 files use Support[ing] Capabilities (incorrect tense)
• 1 file uses Adjacent Capabilities (incorrect heading entirely)

Change Supporting Capabilities → Supported Capabilities (19 files)

• automate-coding-standards.md#L55
• automate-database-migrations.md#L98
• automate-infrastructure-management.md#L86
• automate-test-coverage-checks.md#L62
• build-consistent-testing-strategy.md#L112
• check-documentation-consistency.md#L107
• clean-git-history.md#L83
• conduct-code-reviews.md#L84
• create-and-manage-ephemeral-environments.md#L52
• decouple-from-third-parties.md#L65
• lead-a-demonstration.md#L57
• migrate-to-monorepo.md#L50
• open-telemetry-practice.md#L86
• perform-automated-code-analysis.md#L76
• refactor.md#L77
• refactoring-to-clean-architecture.md#L113
• separate-config-from-code.md#L71
• use-spin-to-unearth-problems-and-solutions.md#L38
• version-dependencies.md#L65

Change Adjacent Capabilities → Supported Capabilities (1 file)

• host-crucial-conversation.md#L56