settings: Delete obsolete code related to the rebase-merge lab settings.

rhodecode/controllers/admin/settings.py

@@ -789,13 +789,6 @@ LabSetting = collections.namedtuple(
 # This list has to be kept in sync with the form
 # rhodecode.model.forms.LabsSettingsForm.
 _LAB_SETTINGS = [
-    LabSetting(
-        key='rhodecode_hg_use_rebase_for_merging',
-        type='bool',
-        group=lazy_ugettext('Mercurial server-side merge'),
-        label=lazy_ugettext('Use rebase instead of creating a merge commit when merging via web interface'),
-        help=''  # Do not translate the empty string!
-    ),
     LabSetting(
         key='rhodecode_proxy_subversion_http_requests',
         type='bool',

rhodecode/model/forms.py

@@ -416,7 +416,6 @@ def LabsSettingsForm():
         allow_extra_fields = True
         filter_extra_fields = False
 
-        rhodecode_hg_use_rebase_for_merging = v.StringBoolean(if_missing=False)
         rhodecode_proxy_subversion_http_requests = v.StringBoolean(
             if_missing=False)
         rhodecode_subversion_http_server_url = v.UnicodeString(