[lemmas] Fix comment on public API
[lemmas] Fix comment on public API

After we moved `start_lemma_com` to `vernacentries` the comment on
`start_lemma_with_initialization` needs update.

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