Fixes stack overflow exception in ReadSpectrogram

The changes in a29aad1 introduced a self-calling version of the the ReadSpectrogram method when the overload was simplified.
This led to a stackoverflow and the difficult to debug variable unit test symptom we were seeing.

Work done for #196

src/AudioAnalysisTools/Indices/IndexMatrices.cs

@@ -420,11 +420,6 @@ public static Dictionary<string, double[]> AddDerivedIndices(Dictionary<string,
         /// and the first column contains row/time names.
         /// Note: no rotation of data is done!.
         /// </summary>
-        public static double[,] ReadSpectrogram(FileInfo csvFile, out int binCount)
-        {
-            return ReadSpectrogram(csvFile, out binCount);
-        }
-
         public static double[,] ReadSpectrogram(FileInfo csvFile, out int binCount, TwoDimensionalArray transform = TwoDimensionalArray.None)
         {
             double[,] matrix = Csv.ReadMatrixFromCsv<double>(csvFile, transform);