chore(very_good_flutter_plugin): tighten dependencies

[alestiago]

Description

Resolves #38

Changes derived from generating a project and updating the template made after running:

flutter pub upgrade --tighten -C my_plugin && flutter pub upgrade --tighten -C my_plugin/example && flutter pub upgrade --tighten -C my_plugin_android && flutter pub upgrade --tighten -C my_plugin_ios && flutter pub upgrade --tighten -C my_plugin_linux && flutter pub upgrade --tighten -C my_plugin_macos && flutter pub upgrade --tighten -C my_plugin_platform_interface && flutter pub upgrade --tighten -C my_plugin_web && flutter pub upgrade --tighten -C my_plugin_windows

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore