wp-env schema: Remove leading dot (#62634)

Rename the wp-env schema to not be a dotfile.

Dotfiles have special handling in many systems, including schemastore.org.
Remove the leading dot to improve compatibility.

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Co-authored-by: ajlende <ajlende@git.wordpress.org>
Co-authored-by: t-hamano <wildworks@git.wordpress.org>
Co-authored-by: sirreal <jonsurrell@git.wordpress.org>
Co-authored-by: dd32 <dd32@git.wordpress.org>