fix(mysql2-tav): add 'pretest' command to tav.yml for mysql2 version 3 (open-telemetry#1490)

Author: haddasbronfman

plugins/node/opentelemetry-instrumentation-mysql2/.tav.yml

@@ -1,6 +1,8 @@
 mysql2:
   - versions: <4 >=3.2.0 || 3.1.0 || 3.0.0
     commands: npm run test
+    # Fix missing `test-utils` package
+    pretest: npm run --prefix ../../../ lerna:link
 
   - versions: <3 >=2.3.2 || 2.3.0 || 2.2.5 || 2.1.0
     # Skip 2.3.3 which installs types from git which takes 10m on it's own