37: Add both variants of half open range patterns to the grammar r=lf- a=lf-

This is prompted by
https://github.com/rust-analyzer/rust-analyzer/issues/9779, but it
is not actually a prerequisite of making that one happen as this commit
doesn't change the generated code on the r-a side.

Relevant PR (that does not require this one be merged immediately/a release made): https://github.com/rust-analyzer/rust-analyzer/pull/9780

Co-authored-by: Jade <software@lfcode.ca>