fix: Add end of terms and conditions in LICENSE (#531)

Add missing lines preventing the license_finder gem from detecting
a valid Apache 2.0 license.
diff --git a/LICENSE b/LICENSE
index 67db858..f433b1a 100644
--- a/LICENSE
+++ b/LICENSE
@@ -173,3 +173,5 @@
       defend, and hold each Contributor harmless for any liability
       incurred by, or claims asserted against, such Contributor by reason
       of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS