Do not require Traders for Diaspora

Remove the need to train 3 Traders before researching Diaspora, which
will now be researched directly from the Market instead of the Civic
Center. To compensate, increase cost by +100 food, +200 metal, and
+10 research time, matching the three resources used to produce
Traders, but in smaller quantities.

Fixes #7381

binaries/data/mods/public/simulation/data/technologies/unlock_shared_dropsites.json

@@ -2,20 +2,13 @@
 	"genericName": "Diaspora",
 	"description": "The extension of trade leads to the permanent establishment of storekeepers and their families in foreign countries, allowing them to exploit the wealth of these countries.",
 	"cost": {
-		"food": 200,
+		"food": 300,
 		"wood": 200,
 		"stone": 100,
-		"metal": 100
+		"metal": 300
 	},
-	"requirements": {
-		"entity": {
-			"class": "Trader",
-			"number": 3
-		}
-	},
-	"requirementsTooltip": "Requires three Traders",
 	"icon": "dove.png",
-	"researchTime": 40,
+	"researchTime": 50,
 	"tooltip": "Allows using allied dropsites.",
 	"modifications": [
 		{ "value": "Player/sharedDropsites", "replace": true }

binaries/data/mods/public/simulation/templates/template_structure_civic_civil_centre.xml

@@ -100,7 +100,6 @@
       phase_town_{civ}
       phase_city_{civ}
       unlock_shared_los
-      unlock_shared_dropsites
       archery_tradition
       hoplite_tradition
       hellenistic_metropolis

binaries/data/mods/public/simulation/templates/template_structure_economic_market.xml

@@ -49,6 +49,7 @@
       trade_gain_02
       trade_commercial_treaty
       unlock_shared_los
+      unlock_shared_dropsites
     </Technologies>
   </Researcher>
   <Sound>