chore: Remove lerna (#2116)

**What**
- Removes `lerna` as we are now using `changesets` + Turborepo to handle builds and releases

scripts/generate-fixtures.sh

@@ -1,20 +0,0 @@
-#!/bin/bash
-
-FIXTURE_PATTERN=$1
-
-lerna run build
-
-medusa-dev --set-path-to-repo .
-
-cd docs-util/fixture-gen
-
-medusa-dev --force-install --scan-once
-
-cd ../..
-
-if [ "$FIXTURE_PATTERN" ]; then
-  yarn test:fixtures -t $FIXTURE_PATTERN
-else
-  yarn test:fixtures
-fi
-