sns: single value filter has no reason to override capacity

code/espurna/filters/LastFilter.h

@@ -13,10 +13,6 @@ public:
         _value = value;
     }
 
-    size_t capacity() const override {
-        return 1;
-    }
-
     void reset() override {
         _value = 0;
     }

code/espurna/filters/MaxFilter.h

@@ -15,10 +15,6 @@ public:
         _value = std::max(value, _value);
     }
 
-    size_t capacity() const {
-        return 1;
-    }
-
     void reset() override {
         _value = 0;
     }