pjsip/alembic: Fix definition of qualify_timeout

A recent commit set qualify_timeout to Decimal which isn't supported.
This path corrects it to Float.

Change-Id: I038f5274ba8cb60f8518a5845ce448d49306aadf

contrib/ast-db-manage/config/versions/423f34ad36e2_fix_pjsip_qualify_ti.py

@@ -15,8 +15,8 @@ import sqlalchemy as sa
 
 
 def upgrade():
-    op.alter_column('ps_aors', 'qualify_timeout', type_=sa.Decimal)
+    op.alter_column('ps_aors', 'qualify_timeout', type_=sa.Float)
-    op.alter_column('ps_contacts', 'qualify_timeout', type_=sa.Decimal)
+    op.alter_column('ps_contacts', 'qualify_timeout', type_=sa.Float)
     pass