pyproject: remove redundant "unused imports" comments

Since we refer to ruff rules by names

src/bonsai/pyproject.toml

@@ -33,7 +33,7 @@ exclude = ["test*"]
 [tool.ruff]
 extend = "../../pyproject.toml"
 lint.extend-select = [
-  "unused-import",  # unused imports
+  "unused-import",
 ]
 
 [tool.ruff.lint.isort]

src/bonsai/test/pyproject.toml

@@ -1,5 +1,5 @@
 [tool.ruff]
 extend = "../pyproject.toml"
 lint.ignore = [
-  "unused-import",  # unused imports
+  "unused-import",
 ]