Use form with normal-sized button on follows show pages

[AntonKhorev]

Originally the make/remove friend pages contained a form:

openstreetmap-website/app/views/friendships/make_friend.html.erb

Lines 5 to 10 in 1732325

	<%= bootstrap_form_tag do |f| %>
	<% if params[:referer] -%>
	<%= f.hidden_field :referer, :value => params[:referer] %>
	<% end -%>
	<%= f.primary t(".button") %>
	<% end %>

#5261 replaces these two pages with one /user/:user/follow page. That have doesn't have a form. Instead it has a link styled as a button. This is probably because there were multiple changes to paths during the development of that PR. But I don't know why it shouldn't be a true button with the paths we eventually settled on. Also the link has a small button css class on it. I don't know why the button that is the only thing on the page should be small. Probably it was a copypasted code from subscribe/unsubscribe buttons or something similar.

Before:

After:

[gravitystorm]

Merged, thanks!