AllowSynchronousIO = false AND CacheTagHelper

CacheTagHelper doesn't work without AllowSynchronousIO = true;

Relevant Stacktrace:
```
System.InvalidOperationException: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpResponseStream.Write(Byte[] buffer, Int32 offset, Int32 count)
at System.IO.Compression.DeflateStream.WriteDeflaterOutput()
at System.IO.Compression.DeflateStream.WriteCore(ReadOnlySpan`1 buffer)
at System.IO.Compression.DeflateStream.Write(Byte[] array, Int32 offset, Int32 count)
at System.IO.Compression.GZipStream.Write(Byte[] array, Int32 offset, Int32 count)
at Microsoft.AspNetCore.ResponseCompression.ResponseCompressionBody.Write(Byte[] buffer, Int32 offset, Int32 count)
at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.FlushInternal(Boolean flushEncoder)
at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.Write(Char[] values, Int32 index, Int32 count)
at Microsoft.AspNetCore.Mvc.TagHelpers.CacheTagHelper.CharBufferHtmlContent.WriteTo(TextWriter writer, HtmlEncoder encoder)
```
https://github.com/aspnet/Mvc/blob/04ce6cae44fb0cb11470c21769d41e3f8088e8aa/src/Microsoft.AspNetCore.Mvc.TagHelpers/CacheTagHelper.cs#L264