The spotless gradle plugin fails on some common Java 16 syntax

[kwvanderlinde]

Describe the bug
Even though MapTool targets Java 16, the spotless plugin 5.2.0 does not support some common Java 16 syntax. This causes the plugin to error out as though invalid syntax was encountered, even though it is valid Java. E.g. instanceof patterns like this:

if (object instanceof String string) {
   ...
}

This prevents the use of some Java 16 features in MapTool.

To Reproduce
Steps to reproduce the behavior:

1. Add an instanceof patterns to the codebase.
2. Run spotlessCheck from gradle.
3. Observe an error message with the cause error: ')' expected

Expected behavior
instanceof patterns and other Java 16 syntax is accepted so it can be used in MapTool.

MapTool Info

• Version: develop
• Install:

Desktop (please complete the following information):

• OS: Linux Mint
• Version 20

Additional context
We're using spotless plugin version 5.2.0, but there is already version 5.14.3 available which seems to support Java 16 syntax.

[Phergus]

Tested described instanceof pattern issue. Now passes spotless. No other issues seen.