angularjs: Fix plain icon

[why]
There are two problems with the plain svg:
- The top of the 'A' consists of a lot of nodes that have a very complex
  outline, while in reality it should only be one sharp node
- The 'A' outline is not closed

[how]
Remove superfluous nodes from outline and close it.

Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>

Author: Finii