Update SizeGetters to only account for dynamic memory usage.

src/parser/Iri.h

@@ -52,9 +52,7 @@ class Iri {
   // Calculate the memory usage of the `Iri` string. This might overestimate the
   // memory usage as this does not currently take into account small string
   // optimization of `std::string`
-  size_t getDynamicMemoryUsage() const {
-    return sizeof(std::string) + iri_.capacity();
-  }
+  size_t getDynamicMemoryUsage() const { return iri_.capacity(); }
 };
 
 }  // namespace ad_utility::triple_component

src/parser/Literal.h

@@ -95,8 +95,6 @@ class Literal {
   // Calculate the memory usage of the `Literal` string. This might overestimate
   // the memory usage as this does not currently take into account small string
   // optimization of `std::string`
-  size_t getDynamicMemoryUsage() const {
-    return sizeof(std::string) + content_.capacity();
-  }
+  size_t getDynamicMemoryUsage() const { return content_.capacity(); }
 };
 }  // namespace ad_utility::triple_component