fix build errors (#957)

A few samples weren't caught in the first PR.

contributes to dotnet/dotnet-api-docs#2553

Author: BillWagner

snippets/csharp/VS_Snippets_CLR_System/system.String.Format/cs/qa-interpolated2.cs

@@ -2,9 +2,9 @@
 
 public class Example
 {
-   // <SnippetQAInterpolated2>
    public static void Main()
    {
+      // <SnippetQAInterpolated2>
       string[] names = { "Balto", "Vanya", "Dakota", "Samuel", "Koani", "Yiska", "Yuma" };
       string output = $"{names[0]}, {names[1]}, {names[2]}, {names[3]}, {names[4]}, " + 
                       $"{names[5]}, {names[6]}";  

snippets/csharp/VS_Snippets_CLR_System/system.String.Format/cs/qa26.cs

@@ -11,13 +11,13 @@ public static void Main()
          result = String.Format("{0,12:C2}   {0,12:E3}   {0,12:F4}   {0,12:N3}  {1,12:P2}\n",
                                 Convert.ToDouble(value), Convert.ToDouble(value) / 10000);
          Console.WriteLine(result);
+      }                           
       // The example displays output like the following:
       //       $1,603.00     1.603E+003      1603.0000      1,603.000       16.03 %
       //    
       //       $1,794.68     1.795E+003      1794.6824      1,794.682       17.95 %
       //    
       //      $15,436.14     1.544E+004     15436.1400     15,436.140      154.36 %
       // </Snippet26>
-      }                           
    }
 }

snippets/csharp/VS_Snippets_CLR_System/system.String.Format/cs/starting3.cs

@@ -8,7 +8,7 @@ public static void Main()
        // <Snippet33>
        int[] years = { 2013, 2014, 2015 };
        int[] population = { 1025632, 1105967, 1148203 };
-       var sb = new StringBuilder();
+       var sb = new System.Text.StringBuilder();
        sb.Append(String.Format("{0,6} {1,15}\n\n", "Year", "Population"));
        for (int index = 0; index < years.Length; index++)
           sb.Append(String.Format("{0,6} {1,15:N0}\n", years[index], population[index]));

snippets/csharp/VS_Snippets_CLR_System/system.String.Format2/cs/Example2.cs

@@ -14,7 +14,7 @@ public static void Main()
       Console.WriteLine("Culture     Date                                Value\n");
       foreach (string cultureName in cultureNames)
       {
-         CultureInfo culture = new CultureInfo(cultureName);
+         System.Globalization.CultureInfo culture = new System.Globalization.CultureInfo(cultureName);
          string output = String.Format(culture, "{0,-11} {1,-35:D} {2:N}", 
                                        culture.Name, dateToDisplay, value);
          Console.WriteLine(output);