Update contribute.md file for latest IntelliJ Versions

[MariusBrill]

This change is 

[heiko-holz]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @MariusBrill)

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CONTRIBUTING.md line 9 at r1 (raw file):

We also recommend installing the **Gradle Plugin** and the **[Save Actions Plugin](https://plugins.jetbrains.com/plugin/7642-save-actions)** (Note that you need to make sure your [keymap is up to date](https://youtrack.jetbrains.com/issue/IDEA-277194) for the plugin to work properly).

For IntelliJ 203.* or older, we also advise you to use the **[Lombok Plugin](https://plugins.jetbrains.com/plugin/6317-lombok-plugin)**.

the Lombok Plugin is actually needed for the development of inspectIT Ocelot.

Maybe it's more suitable to say that

You also need the Lombok Plugin. For IntelliJ 203.* and older, you need to manually install it. For IntelliJ XX.* and newer, the Lombok Plugin is bundled in the IDE.

[codecov]

Codecov Report

Merging #1417 (46268d4) into master (3bff0ca) will increase coverage by 0.07%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1417      +/-   ##
============================================
+ Coverage     81.20%   81.27%   +0.07%     
  Complexity     2109     2109              
============================================
  Files           215      215              
  Lines          6691     6691              
  Branches        785      785              
============================================
+ Hits           5433     5438       +5     
+ Misses          955      950       -5     
  Partials        303      303              

Impacted Files	Coverage Δ
...nspectit/ocelot/core/utils/HighPrecisionTimer.java	90.62% <0.00%> (+1.56%)	⬆️
...in/java/rocks/inspectit/ocelot/core/AgentImpl.java	71.43% <0.00%> (+8.16%)	⬆️

[heiko-holz]

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @MariusBrill)