Update cake monorepo to v6

Author: renovate[bot]

src/Cake.Npm.Tests/Cake.Npm.Tests.csproj

@@ -10,8 +10,8 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Cake.Core" Version="5.0.0" />
-    <PackageReference Include="Cake.Testing" Version="5.0.0" />
+    <PackageReference Include="Cake.Core" Version="6.1.0" />
+    <PackageReference Include="Cake.Testing" Version="6.1.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
     <PackageReference Include="Shouldly" Version="4.3.0" />
     <PackageReference Include="xunit" Version="2.9.3" />

src/Cake.Npm/Cake.Npm.csproj

@@ -20,6 +20,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Cake.Core" Version="5.0.0" PrivateAssets="All" />
+    <PackageReference Include="Cake.Core" Version="6.1.0" PrivateAssets="All" />
   </ItemGroup>
 </Project>