fix: pkg_manifest_minimal example (#1458)

As pointed out #1429, the `pkg_manifest_minimal` example was calling
`ComplexClass.greet()` and printing the result, but the function did not
return anything. Instead, it was printing in `greet()` function. That
was not the original intent. I updated `ComplexClass.greet()` to return
the greeting so that the executable can print it. I also added a check
in `do_test` to confirm that it was being output properly. All of this
was a miss on my part.

Thanks to @0xLucasMarcal  for pointing this.

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: cgrindel

examples/pkg_manifest_minimal/do_test

@@ -24,6 +24,7 @@ assert_match() {
 # Run MyExecutable target
 output="$("${bazel}" run //Sources/MyExecutable)"
 assert_match "Good morning, World!" "${output}"
+assert_match "Olivia .* 30 years old" "${output}"
 
 # Run old-style executable in my_local_package
 output="$("${bazel}" run @swiftpkg_my_local_package//:print-greeting)"

examples/pkg_manifest_minimal/third_party/NotThatAmazingModule/Sources/NotThatAmazingModule/NotThatAmazingModule.swift

@@ -11,8 +11,8 @@ public class ComplexClass {
         self.favoriteColors = favoriteColors
     }
 
-    public func greet() {
-        print("Hello, my name is \(name) and I'm \(age) years old.")
+    public func greet() -> String {
+        return "Hello, my name is \(name) and I'm \(age) years old."
     }
 
     public func addFavoriteColor(color: String) {