Fix case in doc_valid_idents
Fix case in doc_valid_idents

BibTeX and BibLaTeX use the usual capitalization of TeX tools:
- https://www.ctan.org/pkg/bibtex
- https://www.ctan.org/pkg/biblatex
aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust