Update "Unnamed Classes and Instance Main Methods (JEP 445)"

[marchof]

I would like to propose the following improvement on this page:

• The feature was finalized in JEP 456
• For consistency with the other feature articles do not use a JEP number in the file name
• There is a typo in the JEP reference at the bottom: "JEP 445: String Unnamed Patterns and Variables (Preview), OpenJDK"