SELECT so.line, sy.synonym_name
FROM all_source so, all_synonyms sy
WHERE so.owner = <the owner>
  AND so.name = <package name>
  AND so.type = 'PACKAGE BODY'
  AND instr(so.line, sy.synonym_name) != 0
ORDER BY 1, 2
/

SELECT so.line, sy.synonym_owner, sy.synonym_name
FROM all_source so, 
     ( SELECT referenced_owner synonym_owner, referenced_name synonym_name 
       FROM all_dependencies d
       WHERE d.owner = <the owner>
         AND d.name = <package name>
         AND d.type = 'PACKAGE BODY'
         AND d.referenced_type = 'SYNONYM'
     ) s
WHERE so.owner = <the owner>
  AND so.name = <package name>
  AND so.type = 'PACKAGE BODY'
  AND instr(so.line, sy.synonym_name) != 0
ORDER BY 1, 2
/

SQL> create synonym s1 for s2;

Synonym created.

SQL> create synonym s2 for s1;

Synonym created.

SQL> select s1.owner,
            s1.synonym_name,
            s1.table_owner,
            s1.table_name,
            s2.owner,
            s2.synonym_name,
            s2.table_owner,
            s2.table_name
     from   dba_synonyms s1 join dba_synonyms s2
              on s1.synonym_name=s2.table_name
                 and s1.owner=s2.table_owner
     where  s1.synonym_name=s2.table_name
            and s1.table_name=s2.synonym_name;


OWNER    SYNONYM_NAME       TABLE_OWNER        TABLE_NAME  OWNER     SYNONYM_NAME      TABLE_OWNER       TABLE_NAME
------ ---------------- ---------------- ---------------- ------ ---------------- ---------------- ----------------
TINUS  S1               TINUS            S2               TINUS  S2               TINUS            S1
TINUS  S2               TINUS            S1               TINUS  S1               TINUS            S2

SQL> 

SQL>