This PR upgrades `tree-sitter-php` to v0.21.1. Here is the diff between our current version and this version: https://github.com/tree-sitter/tree-sitter-php/compare/d43130fd1525301e9826f420c5393a4d169819fc...29a49d3a53353444ee2226e2efa140fec69dd3e0 The primary impetus for this change is to get this change that adds the `license` field to the `Cargo.toml`: https://github.com/tree-sitter/tree-sitter-php/pull/193 This will silence the warning that is shown when running `script/generate-licenses`. Release Notes: - Upgraded `tree-sitter-php` to v0.21.1.