infra: update to pathspec for 'git grep' in lint check (#18178)

**Description:** Update to the pathspec for 'git grep' in lint check in
the Makefile
**Issue:** The pathspec {docs/docs,templates,cookbook} is not handled
correctly leading to the error during 'make lint' -
"fatal: ambiguous argument '{docs/docs,templates,cookbook}': unknown
revision or path not in the working tree."
See changes made in https://github.com/langchain-ai/langchain/pull/18058

Co-authored-by: Erick Friis <erick@langchain.dev>

Makefile

@@ -50,7 +50,7 @@ lint lint_package lint_tests:
 	poetry run ruff docs templates cookbook
 	poetry run ruff format docs templates cookbook --diff
 	poetry run ruff --select I docs templates cookbook
-	git grep 'from langchain import' {docs/docs,templates,cookbook} | grep -vE 'from langchain import (hub)' && exit 1 || exit 0
+	git grep 'from langchain import' docs/docs templates cookbook | grep -vE 'from langchain import (hub)' && exit 1 || exit 0
 
 format format_diff:
 	poetry run ruff format docs templates cookbook