maint: Remove features deprecated in Octave 8.

* ov-base.h: Remove extern declaration for Vsparse_auto_mutate.

* ov-base.cc (bool Vsparse_auto_mutate): Remove static variable.

* scripts/deprecated/shift.m: Deleted.

* scripts/deprecated/sparse_auto_mutate.m: Deleted.

* scripts/deprecated/module.mk: Remove shift.m and sparse_auto_mutate.m from
build system.

libinterp/octave-value/ov-base.cc

@@ -99,9 +99,6 @@ std::string btyp_class_name[btyp_num_types+1] =
 DEFINE_OV_TYPEID_FUNCTIONS_AND_DATA (octave_base_value,
                                      "<unknown type>", "unknown");
 
-// DEPRECATED in Octave 8.
-bool Vsparse_auto_mutate = false;
-
 #if defined (HAVE_PRAGMA_GCC_DIAGNOSTIC)
    // Disable this warning for the use of the "count" member variable in
    // the default constructor.  Push the current state so we can restore

libinterp/octave-value/ov-base.h

@@ -1010,9 +1010,6 @@ octave_base_dld_value : public octave_base_value
   octave::auto_shlib m_containing_dynamic_library;
 };
 
-OCTAVE_DEPRECATED (8, "Vsparse_auto_mutate is obsolete and is now always false")
-extern OCTINTERP_API bool Vsparse_auto_mutate;
-
 // Utility function to convert C++ arguments used in subsref/subsasgn into an
 // octave_value_list object that can be used to call a function/method in the
 // interpreter.

scripts/deprecated/module.mk

@@ -1,9 +1,7 @@
 FCN_FILE_DIRS += %reldir%
 
 %canon_reldir%_FCN_FILES = \
-  %reldir%/.oct-config \
-  %reldir%/shift.m \
-  %reldir%/sparse_auto_mutate.m
+  %reldir%/.oct-config
 
 %canon_reldir%dir = $(fcnfiledir)/deprecated