Disable todotxt grammar for files named "todo.txt"

The file name is too common and can unintentionally conflict. Users
should manually opt in.

Fixes helix-editor#10113

languages.toml

@@ -3135,7 +3135,8 @@ source = { git = "https://github.com/kylegoetz/tree-sitter-unison", rev = "1f505
 [[language]]
 name = "todotxt"
 scope = "text.todotxt"
-file-types = [{ glob = "todo.txt" }, { glob = "*.todo.txt" }, "todotxt"]
+# glob = "todo.txt" is too common and can conflict regular files, define in user config if necessary
+file-types = [{ glob = "*.todo.txt" }, "todotxt"]
 formatter = { command = "sort" }
 auto-format = true