Drop `strings.HasPrefix` when guarding `strings.TrimPrefix`.

There is no need to check as `TrimPrefix` does nothing if the prefix
doesn't match (see https://pkg.go.dev/strings#TrimPrefix).

Bug: 193425964
Test: m nothing
Change-Id: Ieb82e72a471800e29eb6bb54308041a9ab4173e5
diff --git a/java/robolectric.go b/java/robolectric.go
index 00f233e..a37a118 100644
--- a/java/robolectric.go
+++ b/java/robolectric.go
@@ -179,7 +179,7 @@
 			continue
 		} else if strings.HasSuffix(s, "/BaseRobolectricTest.java") {
 			continue
-		} else if strings.HasPrefix(s, "src/") {
+		} else {
 			s = strings.TrimPrefix(s, "src/")
 		}
 		r.tests = append(r.tests, s)