Deprecate tourism=picnic_table (#1104)

data/deprecated.json

@@ -1685,6 +1685,10 @@
     "old": {"tourism": "bed_and_breakfast"},
     "replace": {"tourism": "guest_house", "guest_house": "bed_and_breakfast"}
   },
+  {
+    "old": {"tourism": "picnic_table"},
+    "replace": {"leisure": "picnic_table"}
+  },
   {
     "old": {"tower:type": "power"},
     "replace": {"power": "tower"}