how to alter sequence in db2 stored procedure by another user
Effect of DYNAMICRULES bind option on dynamic SQL

You must set the DYNAMICRULES bind option to BIND before the routine creation to make dynamic sql statements of the routine execute with the routine creator authorization. They are executed with authorization of a user who runs the routine otherwise.
You can do it by calling the following statement before the CREATE OR REPLACE PROCEDURE statement in the same session:  

CALL SET_ROUTINE_OPTS('DYNAMICRULES BIND')


But you are not able to execute dynamically the following statements with such a bind option as described in Table 2. Definitions of Dynamic SQL Statement Behaviors:  

GRANT, REVOKE, ALTER, CREATE, DROP, COMMENT ON, RENAME, SET INTEGRITY, and SET EVENT MONITOR STATE


This means, that you are not able to run dynamically ALTER SEQUENCE with an authorization different from the invoker's one.
You may grant ALTER privilege on sequence to your developer to resolve the issue.