Fix not showing errors for invalid contact uploads

This code should behave the same way as other CSV uploads [1],
but we had to write it in a hurry [2] and the way we show an
error with the upload field was based off that for PDF uploads,
where we show custom button text instead of an error [3].

This fixes the inconsistency, so that we see the same errors
for CSV uploads here as in other parts of the app.

[1]: 6b52735dac/app/templates/views/send.html (L25)
[2]: 1c02476ee7 (diff-aedd12af78c9737f1c3344d2afbb9c00878eccbcc754b2b3d9e6864c2ad2f7c3R32)
[3]: 3b3f74bbf0

app/templates/views/uploads/contact-list/upload.html

@@ -40,8 +40,7 @@
   {{ file_upload(
     form.file,
     allowed_file_extensions=allowed_file_extensions,
-    button_text='Upload your file again' if error else 'Choose file',
-    show_errors=False
+    button_text='Choose file',
   )}}
 </div>