Update Nix highlights

* Switch nix grammar repository location to the new repo. The author
  has transferred the repository to 'nix-community'.
* Capture ':' and '...' as 'punctuation.delimiter'.

languages.toml

@@ -591,7 +591,7 @@ indent = { tab-width = 2, unit = "  " }
 
 [[grammar]]
 name = "nix"
-source = { git = "https://github.com/cstrahan/tree-sitter-nix", rev = "6b71a810c0acd49b980c50fc79092561f7cee307" }
+source = { git = "https://github.com/nix-community/tree-sitter-nix", rev = "6b71a810c0acd49b980c50fc79092561f7cee307" }
 
 [[language]]
 name = "ruby"

runtime/queries/nix/highlights.scm

@@ -95,6 +95,8 @@
   "."
   ","
   "="
+  ":"
+  (ellipses)
 ] @punctuation.delimiter
 
 [