6 files declare their use of Unicode

Bootstrap.php in src/Bootstrap.php
BootstrapDropdown.php in src/Plugin/Preprocess/BootstrapDropdown.php
CdnAsset.php in src/Plugin/Provider/CdnAsset.php
deprecated.php in ./deprecated.php
This contains deprecated functions that will be removed in a future release.
ProviderBase.php in src/Plugin/Provider/ProviderBase.php
ThemeSuggestions.php in src/Plugin/Alter/ThemeSuggestions.php