Downgrade two IDE analysis errors to suggestions

.NET 8.0 suggests quite a few more of these "fixes" which we ought to do, but not quite yet!

Author: andyleejordan

.editorconfig

@@ -155,7 +155,7 @@ dotnet_diagnostic.IDE0026.severity = error
 # IDE0027: Use expression body for accessors
 dotnet_diagnostic.IDE0027.severity = error
 # IDE0028: Use collection initializers
-dotnet_diagnostic.IDE0028.severity = error
+dotnet_diagnostic.IDE0028.severity = suggestion
 # IDE0029: Use coalesce expression (non-nullable types)
 dotnet_diagnostic.IDE0029.severity = error
 # IDE0030: Use coalesce expression (nullable types)
@@ -219,7 +219,7 @@ dotnet_diagnostic.IDE0082.severity = error
 # IDE0083: Use pattern matching (not operator)
 dotnet_diagnostic.IDE0083.severity = error
 # IDE0090: Simplify new expression
-dotnet_diagnostic.IDE0090.severity = error
+dotnet_diagnostic.IDE0090.severity = suggestion
 # IDE0100: Remove unnecessary equality operator
 dotnet_diagnostic.IDE0100.severity = error
 # IDE0110: Remove unnecessary discard