Remove unused dependencies

The dependabot file was matching on tree-sitter crates - that's a relic
from v0.6.0 and lower where grammars were regular dependencies.

The remaining changes are unused crates that were forgotten about during
shuffles like moving path canonicalization from helix-core to
helix-loader (and then again from helix-loader to helix-stdx).

.github/dependabot.yml

@@ -8,9 +8,6 @@ updates:
     schedule:
       interval: "weekly"
     groups:
-      tree-sitter:
-        patterns:
-          - "tree-sitter*"
       rust-dependencies:
         update-types:
           - "minor"