Move requirements into their own directory (#12547)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

format.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
 echo "vLLM linting system has been moved from format.sh to pre-commit hook."
-echo "Please run 'pip install -r requirements-lint.txt', followed by"
+echo "Please run 'pip install -r requirements/lint.txt', followed by"
 echo "'pre-commit install --hook-type pre-commit --hook-type commit-msg' to install the pre-commit hook."
 echo "Then linters will run automatically before each commit."