Remove old GCC<=8 (#20508)

GCC version is always greater than 8

src/Base/swigpyrun.cpp

@@ -31,10 +31,8 @@
 #elif defined(__GNUC__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wmissing-field-initializers"
-#if __GNUC__ >= 8
 #pragma GCC diagnostic ignored "-Wcast-function-type"
 #endif
-#endif
 #include "PyExport.h"
 #include "Exception.h"
 namespace Swig_python

src/Mod/Part/App/GeometryMigrationExtension.cpp

@@ -52,11 +52,7 @@ std::unique_ptr<Part::GeometryExtension> GeometryMigrationExtension::copy() cons
 
     copyAttributes(cpy.get());
 
-#if defined (__GNUC__) && (__GNUC__ <=4)
-    return std::move(cpy);
-#else
     return cpy;
-#endif
 }
 
 PyObject * GeometryMigrationExtension::getPyObject()

src/Mod/Sketcher/App/ExternalGeometryExtension.cpp

@@ -82,11 +82,7 @@ std::unique_ptr<Part::GeometryExtension> ExternalGeometryExtension::copy() const
 
     copyAttributes(cpy.get());
 
-#if defined(__GNUC__) && (__GNUC__ <= 4)
-    return std::move(cpy);
-#else
     return cpy;
-#endif
 }
 
 PyObject* ExternalGeometryExtension::getPyObject()

src/Mod/Sketcher/App/SketchGeometryExtension.cpp

@@ -103,12 +103,7 @@ std::unique_ptr<Part::GeometryExtension> SketchGeometryExtension::copy() const
     auto cpy = std::make_unique<SketchGeometryExtension>();
 
     copyAttributes(cpy.get());
-
-#if defined(__GNUC__) && (__GNUC__ <= 4)
-    return std::move(cpy);
-#else
     return cpy;
-#endif
 }
 
 PyObject* SketchGeometryExtension::getPyObject()

src/Mod/Sketcher/App/SolverGeometryExtension.cpp

@@ -53,12 +53,7 @@ std::unique_ptr<Part::GeometryExtension> SolverGeometryExtension::copy() const
     auto cpy = std::make_unique<SolverGeometryExtension>();
 
     copyAttributes(cpy.get());
-
-#if defined(__GNUC__) && (__GNUC__ <= 4)
-    return std::move(cpy);
-#else
     return cpy;
-#endif
 }
 
 PyObject* SolverGeometryExtension::getPyObject()

src/Mod/Sketcher/Gui/ViewProviderSketchGeometryExtension.cpp

@@ -57,11 +57,7 @@ std::unique_ptr<Part::GeometryExtension> ViewProviderSketchGeometryExtension::co
 
     copyAttributes(cpy.get());
 
-#if defined(__GNUC__) && (__GNUC__ <= 4)
-    return std::move(cpy);
-#else
     return cpy;
-#endif
 }
 
 void ViewProviderSketchGeometryExtension::restoreAttributes(Base::XMLReader& reader)