Remove conversions for old saves (t83)

test/t_weather.js

@@ -8,9 +8,9 @@ const rainInAir = (m) => run(`flyers.filter(f => f.rain && f.m === ${m}).length`
 run('generateWorld(777, 1024, 640, null)');
 check('new worlds have no springs', count(run, run('SPRING')) === 0);
 check('and the same seed still makes the same land', run('surfY[512]') > 0 && run('!!dock()'));
-// an older save with a spring in it: the spring becomes plain rock
+// Loading no longer converts retired spring cells to rock.
 run('globalThis.__s = serializeWorld(); __s.buffers.mat[300 * W + 500] = SPRING; deserializeWorld(__s.meta, __s.buffers);');
-check('springs in older worlds turn into plain rock', run('mat[300 * W + 500]') === run('STONE') && count(run, run('SPRING')) === 0);
+check('loading leaves retired spring cells unchanged', run('mat[300 * W + 500]') === run('SPRING') && count(run, run('SPRING')) === 1);
 
 // steam in the open sky rises into the clouds instead of condensing
 flatWorld(run, 320, 200, 120);