Replace link with button in author_actions

- modified corresponding spec

spec/system/budgets/investments_spec.rb

@@ -1715,7 +1715,7 @@ describe "Budget Investments" do
         within("aside") do
           expect(page).not_to have_content "Author"
           expect(page).not_to have_link "Edit"
-          expect(page).not_to have_link "Remove image"
+          expect(page).not_to have_button "Remove image"
         end
       end
 
@@ -1728,7 +1728,7 @@ describe "Budget Investments" do
         within("aside") do
           expect(page).to have_content "AUTHOR"
           expect(page).to have_link "Edit"
-          expect(page).not_to have_link "Remove image"
+          expect(page).not_to have_button "Remove image"
         end
       end
 
@@ -1742,7 +1742,7 @@ describe "Budget Investments" do
         within("aside") do
           expect(page).to have_content "AUTHOR"
           expect(page).not_to have_link "Edit"
-          expect(page).to have_link "Remove image"
+          expect(page).to have_button "Remove image"
         end
       end
     end