test: fix init script

Author: Alex-pvl

tarantool-shared-resources/tarantool3/init.lua

@@ -66,6 +66,7 @@ box.once('schema', function()
     end)
 
     box.schema.user.grant('user_a', 'read,write', 'space', 'space_a')
+    box.schema.user.grant('user_a', 'execute', 'function', 'box.session.user')
     box.schema.user.grant('user_b', 'read,write', 'space', 'space_b')
     box.schema.user.grant('user_b', 'read', 'space', 'space_a')
     box.schema.user.revoke('user_c', 'session', 'universe')