Fixed typo.

Reported at Transifex.

Signed-off-by: rakekniven <2069590+rakekniven@users.noreply.github.com>

iOSClient/Supporting Files/en.lproj/Localizable.strings

@@ -178,7 +178,7 @@
 "_want_delete_account_"     = "Do you want to delete the account %@";
 "_prevent_http_redirection_"= "The redirection in HTTP is not permitted";
 "_pdf_vertical_"            = "PDF vertical display";
-"_pdf_horizontal_"          = "PDF horizontal Display";
+"_pdf_horizontal_"          = "PDF horizontal display";
 
 /* Background of the file listing view */
 "_use_as_background_"       = "Use it as a background";