[V12 migrations] Fix shadow card mappings

[sophschneider]

Previously, we mapped shadow card experimental values like --p-shadow-card-sm-experimental -> --p-shadow-100 in our migrations and migration guide which aren't actually visually equivalent.

Instead, consumers should be manually migrating to use the Card component instead. Card with the shadow bevel is part of our new design language while the old experimental shadow card values are not.

This token should not be used in a lot of places since it was experimental.

[translation-platform[bot]]

Localization quality issues found

The following issues may affect the quality of localized translations if they are not addressed:

• The value Clear for key Polaris.ActionList.SearchField.clearButtonLabel is very short. Short strings are more likely to be misunderstood by translators without context. Please provide additional context for the translators if possible.
• The value Search for key Polaris.ActionList.SearchField.search is very short. Short strings are more likely to be misunderstood by translators without context. Please provide additional context for the translators if possible.
• The value Search actions for key Polaris.ActionList.SearchField.placeholder is very short. Short strings are more likely to be misunderstood by translators without context. Please provide additional context for the translators if possible.

Please look out for other instances of this issue in your PR and fix them as well if possible.

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