Fix exception messages for Azure App Services logger to say "must" instead of "should"

[Eilon]

Here:

Logging/src/Microsoft.Extensions.Logging.AzureAppServices/Internal/AzureBlobSink.cs

Lines 55 to 62 in 61ff52f

	if (batchSizeLimit <= 0)
	{
	throw new ArgumentOutOfRangeException(nameof(batchSizeLimit), $"{nameof(batchSizeLimit)} should be a positive number.");
	}
	if (period <= TimeSpan.Zero)
	{
	throw new ArgumentOutOfRangeException(nameof(period), $"{nameof(period)} should be longer than zero.");
	}

And here:

Logging/src/Microsoft.Extensions.Logging.AzureAppServices/Internal/FileLoggerProvider.cs

Lines 38 to 45 in 61ff52f

	if (fileSizeLimit <= 0)
	{
	throw new ArgumentOutOfRangeException(nameof(fileSizeLimit), $"{nameof(fileSizeLimit)} should be positive.");
	}
	if (retainedFileCountLimit <= 0)
	{
	throw new ArgumentOutOfRangeException(nameof(retainedFileCountLimit), $"{nameof(retainedFileCountLimit)} should be positive.");
	}

We must change the word should to must.

See https://www.ietf.org/rfc/rfc2119.txt