Remove MemberNotNull to fix build (#6699)

## Summary of changes

Updated VS and MSBuild locally and can no longer build.

## Reason for change

Build wasn't working and I think these are covered as we have nullable
enabled and `MetricsHostname` is get only

## Implementation details

Delete

## Test coverage

Build works now

## Other details
<!-- Fixes #{issue} -->

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Author: bouwkast

tracer/src/Datadog.Trace/Configuration/ExporterSettings.cs

@@ -361,7 +361,6 @@ bool TryGetMetricsUriAndTransport(string metricsUrl, out MetricsTransportSetting
             }
 
 #if NETCOREAPP3_1_OR_GREATER
-            [MemberNotNull(nameof(MetricsHostname))]
             bool SetUds(string unixSocket, string original, string absoluteUri, string? source, out MetricsTransportSettings settings)
             {
                 // Only called in the constructor;
@@ -385,7 +384,6 @@ bool SetUds(string unixSocket, string original, string absoluteUri, string? sour
                 return probablyValid;
             }
 #endif
-            [MemberNotNull(nameof(MetricsHostname))]
             bool SetUdp(string hostname, string? hostnameSource, int port, string? portSource, out MetricsTransportSettings settings)
             {
                 var probablyValid = true;