ci: replace special chars (#799)

Author: v1v

.ci/Jenkinsfile

@@ -5,7 +5,7 @@
 pipeline {
   agent { label 'ubuntu-20 && immutable' }
   environment {
-    BRANCH_NAME_LOWER_CASE = "${env.BRANCH_NAME.toLowerCase()}"
+    BRANCH_NAME_LOWER_CASE = "${env.BRANCH_NAME.toLowerCase().replaceAll('[^a-z0-9-]', '-')}"
     CREATED_DATE = "${new Date().getTime()}"
     ENVIRONMENT = "ci"
     REPO = "elastic-package"