[meta] Add ltac2 information to META.
[meta] Add ltac2 information to META.

Closes #11225 , we use a bit of a hack due to the way the Makefile
installs this plugin.

coq/coq,Zimmi48/coq,coq/coq,JasonGross/coq,ejgallego/coq,Zimmi48/coq,ejgallego/coq,JasonGross/coq,gares/coq,Matafou/coq,ejgallego/coq,SkySkimmer/coq,SkySkimmer/coq,coq/coq,Zimmi48/coq,JasonGross/coq,silene/coq,ejgallego/coq,SkySkimmer/coq,Zimmi48/coq,gares/coq,JasonGross/coq,gares/coq,Matafou/coq,SkySkimmer/coq,silene/coq,gares/coq,silene/coq,coq/coq,Matafou/coq,gares/coq