git: openjdk/jdk-sandbox: jdk.javadoc/snippets: Add missing imports to MapSnippets.java

[duke]

Changeset: 3f3213e1
Author:    pavelrappo <pavel.rappo at gmail.com>
Date:      2021-05-06 20:28:40 +0000
URL:       https://git.openjdk.java.net/jdk-sandbox/commit/3f3213e1d69de94affd4ca225efb100c69567afe

Add missing imports to MapSnippets.java

Many thanks to Jon Gibbons, who was able to quickly figure out and fix in the previous commit ("Exclude snippet-files from java.base Java.gmk") the issue where OpenJDK build complained about an unnamed package if MapSnippets.java was stripped off `package java.util;` and put directly under the `snippet-files` directory. Thanks to that fix, creating a package structure under `snippet-files` is now not a requirement, but an option.

Since MapSnippets.java no longer belongs to java.util, we need to import usages from that package.

! src/java.base/share/classes/java/util/snippet-files/MapSnippets.java