Change zoom level for NE states/provinces (#1184)

Fixes #1055 

This PR moves Natural Earth zoom 7.7 boundary lines into zoom 4.

> Hi, thank you for PR. In github-actions statistics there is a pretty high size increase in zooms 3, 2, 1, which are using data from zoom 4. Maybe keep your change to move `min_zoom <= 7.7` just for zoom 4, but for zoom 3 add a condition `min_zoom <= 7` (that subsequently the condition bubbles into zoom 2 and 1). What do you think?

I agree that this makes sense, and thank you for pointing it out.  It didn't occur to me that the zoom 1-3 tables were unbounded.  I made the change to pull the `min_zoom` column into the zoom 4 generalized table and filter for `min_zoom< 7`.

With this change, here is Algeria, zoom 3:
![image](https://user-images.githubusercontent.com/3254090/130368190-616891f4-4a53-4780-926b-561007291f33.png)

Algeria, zoom 4:
![image](https://user-images.githubusercontent.com/3254090/130368194-d4e722bb-559b-4e2a-bb82-a5d1bd95985c.png)

layers/boundary/boundary.sql

@@ -228,9 +228,10 @@ SELECT ST_Simplify(geometry, ZRes(6)) as geometry,
        FALSE AS disputed,
        NULL::text AS disputed_name,
        NULL::text AS claimed_by,
-       FALSE AS maritime
+       FALSE AS maritime,
+       min_zoom
 FROM ne_10m_admin_1_states_provinces_lines
-WHERE min_zoom <= 7
+WHERE min_zoom <= 7.7
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS ne_10m_admin_1_states_provinces_lines_gen_z4_idx ON ne_10m_admin_1_states_provinces_lines_gen_z4 USING gist (geometry);
 
@@ -246,6 +247,7 @@ SELECT ST_Simplify(geometry, ZRes(5)) as geometry,
        claimed_by,
        maritime
 FROM ne_10m_admin_1_states_provinces_lines_gen_z4
+WHERE min_zoom <= 7
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS ne_10m_admin_1_states_provinces_lines_gen_z3_idx ON ne_10m_admin_1_states_provinces_lines_gen_z3 USING gist (geometry);