pam_lastlog2: remove symbol that doesn't exist from version script

otherwise ld.lld by default errors with
ld: error: version script assignment of 'global' to symbol 'pam_sm_chauthtok' failed: symbol not defined

since the symbol is not in the library
diff --git a/pam_lastlog2/src/pam_lastlog2.sym b/pam_lastlog2/src/pam_lastlog2.sym
index 1633155..88ef3e8 100644
--- a/pam_lastlog2/src/pam_lastlog2.sym
+++ b/pam_lastlog2/src/pam_lastlog2.sym
@@ -3,9 +3,8 @@
   global:
     pam_sm_acct_mgmt;
     pam_sm_authenticate;
-    pam_sm_chauthtok;
     pam_sm_close_session;
     pam_sm_open_session;
     pam_sm_setcred;
   local: *;
-};
\ No newline at end of file
+};