chore(deps): update dependency flagsmith to v5.3.0

Author: renovate[bot]

src/OpenFeature.Contrib.Providers.Flagsmith/OpenFeature.Contrib.Providers.Flagsmith.csproj

@@ -19,7 +19,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Flagsmith" Version="5.2.2" />
+    <PackageReference Include="Flagsmith" Version="5.3.0" />
     <PackageReference Include="System.Text.Json" Version="8.0.3" />
   </ItemGroup>