Move flake8 to end. Don't exit script on failure (#7738)

changelog.d/7738.misc

@@ -0,0 +1 @@
+Move `flake8` to the end of `scripts-dev/lint.sh` as it takes the longest and could cause the script to exit early.

scripts-dev/lint.sh

@@ -2,8 +2,8 @@
 #
 # Runs linting scripts over the local Synapse checkout
 # isort - sorts import statements
-# flake8 - lints and finds mistakes
 # black - opinionated code formatter
+# flake8 - lints and finds mistakes
 
 set -e
 
@@ -16,6 +16,6 @@ fi
 
 echo "Linting these locations: $files"
 isort -y -rc $files
-flake8 $files
 python3 -m black $files
 ./scripts-dev/config-lint.sh
+flake8 $files