software/plantuml: update to 1.2020.15.war

Rendering of some diagrams to png is slightly different, images are not
same size

software/plantuml/software.cfg

@@ -27,8 +27,9 @@ output = ${buildout:directory}/${:_buildout_section_name_}
 
 [plantuml.war]
 recipe = slapos.recipe.build:download
-url = https://downloads.sourceforge.net/project/plantuml/1.2018.13/plantuml.1.2018.13.war
-md5sum = cda05c8163237de039d777c197b3d282
+url = https://sourceforge.net/projects/plantuml/files/1.2020.15/plantuml.1.2020.15.war
+md5sum = ed203cb3b90df8f77492fa36ea6490a5
+
 
 [versions]
 slapos.recipe.template = 4.4