STYLE: Remove deprecated function isRelease() from application API

Migration guide is available here:
https://www.slicer.org/wiki/Documentation/Nightly/Developers/Tutorials/MigrationGuide/Slicer#Slicer_4.9:_Application:_isRelease.28.29_function_not_available

git-svn-id: http://svn.slicer.org/Slicer4/trunk@26888 3bd1e089-480b-0410-8dfb-8563597acbee

Author: jcfr

Base/QTCore/qSlicerCoreApplication.cxx

@@ -1007,13 +1007,6 @@ QString qSlicerCoreApplication::releaseType()const
   return QString(Slicer_RELEASE_TYPE);
 }
 
-//-----------------------------------------------------------------------------
-bool qSlicerCoreApplication::isRelease()const
-{
-  qWarning() << Q_FUNC_INFO << "Deprecated: Use releaseType() instead";
-  return this->releaseType() == "Stable";
-}
-
 //-----------------------------------------------------------------------------
 void qSlicerCoreApplication::setMRMLScene(vtkMRMLScene* newMRMLScene)
 {

Base/QTCore/qSlicerCoreApplication.h

@@ -78,7 +78,6 @@ class Q_SLICER_BASE_QTCORE_EXPORT qSlicerCoreApplication : public QApplication
   Q_PROPERTY(QString extensionsInstallPath READ extensionsInstallPath WRITE setExtensionsInstallPath)
   Q_PROPERTY(QString intDir READ intDir CONSTANT)
   Q_PROPERTY(bool isInstalled READ isInstalled CONSTANT)
-  Q_PROPERTY(bool isRelease READ isRelease CONSTANT)
   Q_PROPERTY(QString releaseType READ releaseType CONSTANT)
   Q_PROPERTY(QString repositoryUrl READ repositoryUrl CONSTANT)
   Q_PROPERTY(QString repositoryBranch READ repositoryBranch CONSTANT)
@@ -258,13 +257,6 @@ class Q_SLICER_BASE_QTCORE_EXPORT qSlicerCoreApplication : public QApplication
   /// Release type can be `Experimental`, `Nightly` or `Stable`.
   QString releaseType()const;
 
-  /// \brief Return true if this instance of Slicer is a \a Stable release build.
-  ///
-  /// \deprecated Use `releaseType() == "Stable"` instead.
-  ///
-  /// \sa releaseType()
-  bool isRelease()const;
-
   /// Associate a module with a node type.
   /// It is currently only used for determining which module can edit a specific node.
   /// If multiple modules are registered for the same class then the node widget's