docs: correct CI badge reference

Badge wrongly referenced tree-sitter-c before, changed to tree-sitter-rust

Author: cbueth

README.md

@@ -1,6 +1,6 @@
 # tree-sitter-rust
 
-[![CI](https://github.com/tree-sitter/tree-sitter-c/actions/workflows/ci.yml/badge.svg)](https://github.com/tree-sitter/tree-sitter-c/actions/workflows/ci.yml)
+[![CI](https://github.com/tree-sitter/tree-sitter-rust/actions/workflows/ci.yml/badge.svg)](https://github.com/tree-sitter/tree-sitter-rust/actions/workflows/ci.yml)
 
 Rust grammar for [tree-sitter](https://github.com/tree-sitter/tree-sitter)