Fix typos in TestDiagnosticMessagesImpl.

Change-Id: Id89c4e1705ffbd7ac8603c60ea2b23c64b0dc704
diff --git a/src/test/java/com/android/tools/r8/TestDiagnosticMessagesImpl.java b/src/test/java/com/android/tools/r8/TestDiagnosticMessagesImpl.java
index 43d71b1..15c03dc 100644
--- a/src/test/java/com/android/tools/r8/TestDiagnosticMessagesImpl.java
+++ b/src/test/java/com/android/tools/r8/TestDiagnosticMessagesImpl.java
@@ -91,9 +91,9 @@
     StringBuilder builder = new StringBuilder("No warning matches " + matcher.toString());
     builder.append(System.lineSeparator());
     if (getWarnings().size() == 0) {
-      builder.append("There where no warnings.");
+      builder.append("There were no warnings.");
     } else {
-      builder.append("There where " + getWarnings().size() + " warnings:");
+      builder.append("There were " + getWarnings().size() + " warnings:");
       builder.append(System.lineSeparator());
       for (int i = 0; i < getWarnings().size(); i++) {
         builder.append(getWarnings().get(i).getDiagnosticMessage());