Remove 2 redundant else, according to rule F.56 (#1766)

* Remove 2 redundant else, according to rule F.56

* Remove continue from example code

Update after pull request comment.

CppCoreGuidelines.md

@@ -12595,10 +12595,8 @@ Readability. Error prevention. Efficiency.
         cout << f(v, &v[i]) << '\n';
 
     for (gsl::index i = 0; i < v.size(); ++i) { // body messes with loop variable: can't be a range-for
-        if (i % 2 == 0)
+        if (i % 2 != 0)
-            continue;   // skip even elements
+            cout << v[i] << '\n'; // output odd elements
-        else
-            cout << v[i] << '\n';
     }
 
 A human or a good static analyzer might determine that there really isn't a side effect on `v` in `f(v, &v[i])` so that the loop can be rewritten.
@@ -20386,7 +20384,7 @@ In particular, the single-return rule makes it harder to concentrate error check
     {
         if (x < 0)
             return "negative";
-        else if (x > 0)
+        if (x > 0)
             return "positive";
         return "zero";
     }