fix: adjust MaxGroupMemPrice (#704)

if total amount of memory in group less then 1G
calculatePriceRange will always return range 0..1.

fixes #640

validation/config.go

@@ -26,7 +26,7 @@ type ValConfig struct {
 	MaxGroupStorage int64 `env:"AKASH_MAX_GROUP_STORAGE"   envDefault:"5368709120"` // 5Gi
 
 	MinGroupMemPrice int64 `env:"AKASH_MEM_PRICE_MIN" envDefault:"50"`
-	MaxGroupMemPrice int64 `env:"AKASH_MEM_PRICE_MAX" envDefault:"150"`
+	MaxGroupMemPrice int64 `env:"AKASH_MEM_PRICE_MAX" envDefault:"1048576"`
 }
 
 var defaultConfig = ValConfig{}