Remove unchangeable default_grp from specfiles

Since default_group in specdescription is never modified, remove it as a
class member from the Specfiles class and just write the default.

autospec/specfiles.py

@@ -48,7 +48,6 @@ class Specfile(object):
         self.sources = {"unit": [], "gcov": [], "tmpfile": [], "archive": []}
         self.source_index = {}
         self.default_sum = ""
-        self.default_grp = ""
         self.licenses = []
         self.packages = OrderedDict()
         self.requires = set()
@@ -170,7 +169,7 @@ class Specfile(object):
         Write package summary to spec file
         """
         self._write("Summary  : {}\n".format(self.default_sum.strip()))
-        self._write("Group    : {}\n".format(self.default_grp.strip()))
+        self._write("Group    : Development/Tools\n")
 
     def write_license(self):
         """

tests/test_specfile.py

@@ -70,10 +70,9 @@ class TestSpecfileWrite(unittest.TestCase):
         test write_summary with unstripped summary and group strings
         """
         self.specfile.default_sum = "   This is unstripped summary  "
-        self.specfile.default_grp = " This is unstripped group      "
         self.specfile.write_summary()
         expect = ["Summary  : This is unstripped summary\n",
-                  "Group    : This is unstripped group\n"]
+                  "Group    : Development/Tools\n"]
         self.assertEqual(expect, self.WRITES)
 
     def test_write_license(self):