Legacy blocks were previous locked for removal to avoid unintended
consequences. However, this would lock the ability to move the block within
other e.g. layout blocks and unnecessarily limit merchant customization ability.
Now that we have reverted this decision, merchants could delete this block,
which is likely **not** what they want to do. While we investigate other, more
long-term, solutions, we are adding a warning notice.
Refs woocommerce/woocommerce-blocks#5180. Fixeswoocommerce/woocommerce-blocks#5207.
* Rename legacy blocks to avoid confusion with the term “Template”
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