Enable Style/MultilineIfThen rubocop cop

Do not use then for multi-line if.

See #7478.

.rubocop.yml

@@ -362,7 +362,7 @@ Style/MultilineHashBraceLayout:
 
 # Do not use then for multi-line if/unless.
 Style/MultilineIfThen:
-  Enabled: false
+  Enabled: true
 
 # Checks that the closing brace in a method call is either on the same line as
 # the last method argument, or a new line.

app/models/network/graph.rb

@@ -89,7 +89,7 @@ module Network
         end
       end
 
-      if self.class.max_count / 2 < offset then
+      if self.class.max_count / 2 < offset
         # get max index that commit is displayed in the center.
         offset - self.class.max_count / 2
       else
@@ -130,7 +130,7 @@ module Network
       commit.parents(@map).each do |parent|
         range = commit.time..parent.time
 
-        space = if commit.space >= parent.space then
+        space = if commit.space >= parent.space
                   find_free_parent_space(range, parent.space, -1, commit.space)
                 else
                   find_free_parent_space(range, commit.space, -1, parent.space)
@@ -144,7 +144,7 @@ module Network
     end
 
     def find_free_parent_space(range, space_base, space_step, space_default)
-      if is_overlap?(range, space_default) then
+      if is_overlap?(range, space_default)
         find_free_space(range, space_step, space_base, space_default)
       else
         space_default
@@ -155,7 +155,7 @@ module Network
       range.each do |i|
         if i != range.first &&
           i != range.last &&
-          @commits[i].spaces.include?(overlap_space) then
+          @commits[i].spaces.include?(overlap_space)
 
           return true;
         end
@@ -233,7 +233,7 @@ module Network
       space = space_default
       while reserved.include?(space) do
         space += space_step
-        if space < space_base then
+        if space < space_base
           space_step *= -1
           space = space_base + space_step
         end