fix: fetch grammars from non-reference commits

[jbedard]

Reference commits are often (but not always?) only references and not real commits that can be fetched with the githubusercontent.com URL.

This change removes the --refs filter so real commits are also included, which happen to come first with the current ls-remote sorting so it will use the real commit. This fixes updating of a lot of grammars which are broken today.

For example, with --refs:

> git ls-remote --tags --refs --sort -v:refname https://github.com/tree-sitter/tree-sitter-javascript | head -n5
dc2b73b62f162860cc8b55f51a21833ff98867e5	refs/tags/v0.20.1
efd8cc9ee8eb919c2ca0f0eebaeb8f39557d8a8a	refs/tags/v0.19.0
82dc6525aa91eb2cbbe5fe591a737d4f03138886	refs/tags/v0.16.0
cc57665e632f7d6b55e5b7950896f1bd26e02e43	refs/tags/v0.15.2
8f135e9f6e354c5ade9f038201f968862f1fb7ef	refs/tags/v0.15.1

vs without --refs:

> git ls-remote --tags --sort -v:refname https://github.com/tree-sitter/tree-sitter-javascript | head -n5
f1e5a09b8d02f8209a68249c93f0ad647b228e6e	refs/tags/v0.20.1^{}
dc2b73b62f162860cc8b55f51a21833ff98867e5	refs/tags/v0.20.1
efd8cc9ee8eb919c2ca0f0eebaeb8f39557d8a8a	refs/tags/v0.19.0
92a561dfa76cb5a4aafba16f819c3c9e1227ce83	refs/tags/v0.16.0^{}
82dc6525aa91eb2cbbe5fe591a737d4f03138886	refs/tags/v0.16.0

Note that f1e5a09b8d02f8209a68249c93f0ad647b228e6e is valid but the reference commit dc2b73b62f162860cc8b55f51a21833ff98867e5 is not...

[smacker]

great fix! I encountered this problem before but never had time to look into it. Thank you so much!