use `..=` instead of `...` for range pattern matching

[joekyo]

According to the reference, ... is kept for backwards compatibility.

[joekyo]

It seems that the reference recommend us to use ..=.
While the book only introduces ..., and ..= only appears in the appendix of the book.

book $ rg -F '..='
src/appendix-02-operators.md
42:| `..=` | `..=expr`, `expr..=expr` | Right-inclusive range literal | |

[joekyo]

Oh, even the ..= in the appendix is a range literal operator but not range pattern operator.
So the book doesn't mention about ..= as an inclusive range pattern operator at all.