Bump RestEase to 1.6.4

---
updated-dependencies:
- dependency-name: RestEase
  dependency-version: 1.6.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: RestEase
  dependency-version: 1.6.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

IGDB.Tests/IGDB.Tests.csproj

@@ -15,7 +15,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.CSharp" Version="4.7.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
-    <PackageReference Include="RestEase" Version="1.5.5" />
+    <PackageReference Include="RestEase" Version="1.6.4" />
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />
   </ItemGroup>

IGDB/IGDB.csproj

@@ -37,7 +37,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.CSharp" Version="4.7.0" developmentDependency="true" />
-    <PackageReference Include="RestEase" Version="1.5.5" />
+    <PackageReference Include="RestEase" Version="1.6.4" />
   </ItemGroup>
 
 </Project>