remove executable bit for po files

There is a list of po files, that have executable flag set, what is wrong:

find wiki -perm -u+rwx -type f | grep "\.po$"             
wiki/src/doc/first_steps/upgrade/release_notes.es.po
wiki/src/doc/first_steps/startup_options/mac_spoofing.es.po
wiki/src/doc/first_steps/startup_options/bridge_mode.inline.es.po
wiki/src/security/Numerous_security_holes_in_3.2.es.po
wiki/src/security/Numerous_security_holes_in_3.4.es.po
wiki/src/security/Numerous_security_holes_in_3.0.1.es.po
wiki/src/security/Numerous_security_holes_in_3.1.es.po
wiki/src/security/Numerous_security_holes_in_3.3.es.po
wiki/src/security/Numerous_security_holes_in_3.0.es.po
wiki/src/news/many_hands_make_tails.es.po
wiki/src/news/what_we_accomplished_in_2017.es.po
wiki/src/news/our_plans_for_2018.es.po
wiki/src/news/additional_software_ux_design.es.po
wiki/src/news/veracrypt_ux_design.es.po
wiki/src/news/rescue_3.0.1.es.po
wiki/src/news/reproducible_Tails.es.po
wiki/src/install/clone.es.po
wiki/src/install/inc/steps/restart_first_time.inline.es.po
wiki/src/install/win/usb-download.es.po
wiki/src/install/win/usb-overview.es.po
wiki/src/install/win/usb.es.po
wiki/src/install/mac/clone.es.po
wiki/src/install/mac/dvd-overview.es.po
wiki/src/install/mac/usb.es.po
wiki/src/install/mac/dvd.es.po
wiki/src/install/dvd-download.es.po
wiki/src/install/vm-download.es.po
wiki/src/install/linux/clone-overview.es.po
wiki/src/install/linux/usb.es.po
wiki/src/install/debian/clone-overview.es.po
wiki/src/upgrade/tails-overview.es.po
wiki/src/upgrade/tails.es.po
wiki/src/upgrade/tails-download.es.po
wiki/src/donate.es.po

Related issues

• Related to #15402 (closed)
• Blocks #16209

Original created by @Hefee on 16760 (Redmine)