Suppress SmoothScrollPaneUI.java reference in License file

As part of PR881[1] a file was introduced into the Netbeans sources that came from IntelliJ.

IntelliJ is licensed with Apache License 2.0[2] and so possibly shouldn't be included in the License file.  The Notice though should and is included in the license file as expect.

Not blocking for an Incubation release.

[1]: https://github.com/apache/incubator-netbeans/pull/881

[2]: https://github.com/JetBrains/intellij-community/blob/34b9dfd0585937c3731e06a89554d1dc86f7f235/LICENSE.txt