Change feature names to say "Rodin" instead of "Rodin3"

Rodin 2 is long gone.

de.prob2.disprover.feature/feature.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <feature
       id="de.prob2.disprover.feature"
-      label="ProB for Rodin3 - (Dis)Prover"
+      label="ProB for Rodin - (Dis)Prover"
       version="3.1.2.qualifier"
       provider-name="HHU Düsseldorf STUPS Group">
 

de.prob2.feature/feature.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <feature
       id="de.prob2.feature"
-      label="ProB for Rodin3"
+      label="ProB for Rodin"
       version="3.1.2.qualifier"
       provider-name="HHU Düsseldorf STUPS Group">
 

de.prob2.symbolic.feature/feature.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <feature
       id="de.prob2.symbolic.feature"
-      label="ProB for Rodin3 - Symbolic Constants Support"
+      label="ProB for Rodin - Symbolic Constants Support"
       version="3.1.2.qualifier"
       provider-name="HHU Düsseldorf STUPS Group">