iOS で「会員登録をせずに購入」ボタンの文字が表示されないのを修正

[nanasess]

iOS のデフォルトでは input[type=submit].color: #fff となっているため、添付画像のように 会員登録をせずに購入 ボタンが表示されない

input[type=submit].color: #000 とすることで対応

以下のPRを取り込むことでテストはすべて通ることを確認済
#767

[codecov-commenter]

Codecov Report

Merging #747 (088b4c3) into master (47055de) will not change coverage.
The diff coverage is n/a.

❗ Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the Github App Integration for your organization. Read more.

@@           Coverage Diff           @@
##           master     #747   +/-   ##
=======================================
  Coverage   55.33%   55.33%           
=======================================
  Files          75       75           
  Lines        8902     8902           
=======================================
  Hits         4926     4926           
  Misses       3976     3976           

Flag	Coverage Δ
tests	55.33% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.