[libcalamares] Remove unused parameter for PythonJob

- parameter instanceKey was left over from previous work that
  special-cased the weight of Python modules.
- while here, consistently do `~T() override`

src/libcalamares/PythonJob.cpp

@@ -160,8 +160,7 @@ struct PythonJob::Private
     bp::object m_prettyStatusMessage;
 };
 
-PythonJob::PythonJob( const ModuleSystem::InstanceKey& instance,
-                      const QString& scriptFile,
+PythonJob::PythonJob( const QString& scriptFile,
                       const QString& workingPath,
                       const QVariantMap& moduleConfiguration,
                       QObject* parent )

src/libcalamares/PythonJob.h

@@ -31,12 +31,11 @@ class PythonJob : public Job
 {
     Q_OBJECT
 public:
-    explicit PythonJob( const ModuleSystem::InstanceKey& instance,
-                        const QString& scriptFile,
+    explicit PythonJob( const QString& scriptFile,
                         const QString& workingPath,
                         const QVariantMap& moduleConfiguration = QVariantMap(),
                         QObject* parent = nullptr );
-    virtual ~PythonJob() override;
+    ~PythonJob() override;
 
     QString prettyName() const override;
     QString prettyStatusMessage() const override;

src/libcalamaresui/modulesystem/PythonJobModule.cpp

@@ -40,7 +40,7 @@ PythonJobModule::loadSelf()
         return;
     }
 
-    m_job = Calamares::job_ptr( new PythonJob( instanceKey(), m_scriptFileName, m_workingPath, m_configurationMap ) );
+    m_job = Calamares::job_ptr( new PythonJob( m_scriptFileName, m_workingPath, m_configurationMap ) );
     m_loaded = true;
 }