Upgrade the project to 6.0

.vsconfig

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+{
+  "version": "1.0",
+  "components": [ 
+    "Microsoft.VisualStudio.Workload.ManagedGame"
+  ]
+} 

Assembly-CSharp-Editor.csproj.DotSettings

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+<wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=assets_005Cunitytechnologies/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=assets_005Cunitytechnologies_005Cplayground_005C_005Finternal/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=assets_005Cunitytechnologies_005Cplayground_005C_005Finternal_005Cscripts/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=assets_005Cunitytechnologies_005Cplayground_005C_005Finternal_005F/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

Assembly-CSharp.csproj.DotSettings

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+<wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=assets_005Cunitytechnologies/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=assets_005Cunitytechnologies_005Cplayground_005Cscripts/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=assets_005Cunitytechnologies_005Cplayground_005C_005Finternal/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=assets_005Cunitytechnologies_005Cplayground_005C_005Finternal_005Cscripts/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=assets_005Cunitytechnologies_005Cplayground_005C_005Finternal_005F/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>