Remove symbolic plugin's dependencies on main ProB plugin

The symbolic plugin actually also works on its own. This can be useful
e. g. when loading a Rodin project only in the standalone ProB 2 UI and
not with the ProB Rodin plugin.

de.prob.symbolic/META-INF/MANIFEST.MF

@@ -4,9 +4,7 @@ Bundle-Name: ProB Symbolic Evaluation Support
 Bundle-SymbolicName: de.prob.symbolic;singleton:=true
 Bundle-Version: 7.5.0.qualifier
 Bundle-Activator: de.prob.symbolic.Activator
-Require-Bundle: de.prob.core;bundle-version="[9.5.0,9.6.0)",
- de.prob.ui;bundle-version="[7.5.0,7.6.0)",
- org.eclipse.core.runtime;bundle-version="[3.20.0,4.0.0)",
+Require-Bundle: org.eclipse.core.runtime;bundle-version="[3.20.0,4.0.0)",
  org.eclipse.ui;bundle-version="[3.118.0,4.0.0)",
  org.eventb.core;bundle-version="[3.5.0,4.0.0)",
  org.eventb.ui;bundle-version="[3.5.0,4.0.0)",

de.prob2.symbolic.feature/feature.xml

@@ -228,8 +228,6 @@ litigation.
    </license>
 
    <requires>
-      <import plugin="de.prob.core" version="9.5.0" match="equivalent"/>
-      <import plugin="de.prob.ui" version="7.5.0" match="equivalent"/>
       <import plugin="org.eclipse.core.runtime" version="3.20.0" match="compatible"/>
       <import plugin="org.eclipse.ui" version="3.118.0" match="compatible"/>
       <import plugin="org.eventb.core" version="3.5.0" match="compatible"/>