[adonis_pairwise function] Deprecation notice: Replace vegan::adonis with vegan::adonis2

[Ebedthan]

Dear @vmikk,

I suggest to substitute vegan::adonis with vegan::adonis2 because:

• According to the vegan manual, "adonis2 replaces adonis with extended functionality and completely new internal design"
• vegan::adonis is now deprecated and could be retired entirely in the next vegan version.

I can prepare a PR if needed.

Thanks.

[vmikk]

Hello Anicet!

Thank you for your suggestion! I appreciate your input and your offer to help.
I've taken your advice and updated the package to substitute vegan::adonis with vegan::adonis2.

Thank again!

[vmikk]

The issue has been addressed and closed via commit 9c56246.