Fix typo to html/install/index.php

[nanasess]

fixes #503

[codecov-commenter]

Codecov Report

Merging #504 (a219b09) into master (261ef5d) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #504   +/-   ##
=========================================
  Coverage     46.62%   46.62%           
  Complexity       14       14           
=========================================
  Files            81       81           
  Lines         10580    10580           
=========================================
  Hits           4933     4933           
  Misses         5647     5647           

Flag	Coverage Δ
tests	46.62% <ø> (ø)

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[chihiro-adachi]

@nanasess
テストが落ちているようなのでご確認いただいてもよいでしょうか？

[nanasess]

@chihiro-adachi secure.php.net が落ちていたため、PHPがビルドできていなかったようです。
再実行して通りましたので、よろしくお願いします

[chihiro-adachi]

@nanasess
ありがとうございます。マージしました。