Remove graphs from monitor

[DomGarguilo]

Partially addresses #5091 This pull request includes several changes focused on removing the Flot library and related code from the project, as well as cleaning up unused imports and methods. The most important changes include the removal of Flot references from various license files, the deletion of Flot-related code from the Monitor.java class, and the removal of corresponding REST endpoints in StatisticsResource.java.

Removal of Flot library and related code:

• LICENSE, assemble/src/main/resources/LICENSE, server/monitor/src/main/appended-resources/META-INF/LICENSE: Removed references to the Flot library and its dependencies.
• server/monitor/src/main/resources/org/apache/accumulo/monitor/resources/external/flot/LICENSE.txt: Deleted the Flot license file.

Code cleanup in Monitor.java:

• Removed unused imports and methods related to Flot, including newMaxList, fetchData, and various getter methods for metrics over time.

Removal of REST endpoints in StatisticsResource.java:

• Deleted endpoints that provided metrics over time, such as scan rate, query rate, ingest rate, and cache hit rates.

CSS cleanup:

• Removed CSS rules related to Flot from screen.css.

[DomGarguilo]

All of the other pages look the same except the home page which no longer has the graphs: