Change the machine name of header image on donate page.

As per code review feedback to remove confusion.

Issue #48275

content/donate/contents.lr

@@ -82,8 +82,8 @@ tshirt_perk_monthly_label: T-Shirt
 ---
 tshirt_perk_monthly_image: /static/images/donate/t-shirt-take-back-internet.png
 ---
-image: /static/images/donate/donate-header.png
+header_image: /static/images/donate/donate-header.png
 ---
-success_redirect_url:
+success_redirect_url: 
 ---
 counter: yes

lego @ 83db20ae

-Subproject commit 3e7019ee37daa80770cfd986bd4a5bfc01b58103
+Subproject commit 83db20ae1a58f4d533c03ce890eb025f4830f0b2

models/donate-form.ini

@@ -36,7 +36,7 @@ translate = False
 label = Body
 type = markdown
 
-[fields.image]
+[fields.header_image]
 label = Header Image (centered)
 type = string