bob: fix if-statements example code (#2182)

exercises/practice/bob/.approaches/if/content.md

@@ -2,6 +2,7 @@
 
 ```csharp
 using System.Linq;
+
 public static class Bob
 {
     public static string Response(string message)
@@ -21,17 +22,17 @@ public static class Bob
         return "Whatever.";
     }
 
-    private bool IsSilence(string message)
+    private static bool IsSilence(string message)
     {
         return string.IsNullOrWhiteSpace(message);
     }
 
-    private bool IsYell(string message)
+    private static bool IsYell(string message)
     {
         return message.Any(char.IsLetter) && message.ToUpperInvariant() == message;
     }
 
-    private bool IsQuestion(string message)
+    private static bool IsQuestion(string message)
     {
         return message.TrimEnd().EndsWith("?");
     }
@@ -97,14 +98,14 @@ Your team may choose to overrule them.
 When the body of a function is a single expression, the function can be implemented as a [member-bodied expression][member-bodied-expressions], like so
 
 ```csharp
-private bool IsSilence(string message) =>
+private static bool IsSilence(string message) =>
     string.IsNullOrWhiteSpace(message);
 ```
 
 or
 
 ```csharp
-private bool IsSilence(string message) => string.IsNullOrWhiteSpace(message);
+private static bool IsSilence(string message) => string.IsNullOrWhiteSpace(message);
 ```
 
 A [ternary operator][ternary operator] can be used to shorten the code and make the logic more efficient, like so

exercises/practice/bob/.approaches/introduction.md

@@ -45,17 +45,17 @@ public static string Response(string message)
     return "Whatever.";
 }
 
-private bool IsSilence(string message)
+private static bool IsSilence(string message)
 {
     return string.IsNullOrWhiteSpace(message);
 }
 
-private bool IsYell(string message)
+private static bool IsYell(string message)
 {
     return message.Any(char.IsLetter) && message.ToUpperInvariant() == message;
 }
 
-private bool IsQuestion(string message)
+private static bool IsQuestion(string message)
 {
     return message.TrimEnd().EndsWith("?");
 }