[IMPROVEMENT] Japanese localization

[Haruka319]

@RocketChat/ios

Hello,
I tried to improve some of the Japanese translations on RocketChat for Hacktoberfest.
I hope it helps the app.

[CLAassistant]

All committers have signed the CLA.

[CLAassistant]

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[codecov]

Codecov Report

Merging #2777 into develop will decrease coverage by 0.95%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #2777      +/-   ##
===========================================
- Coverage    46.28%   45.32%   -0.96%     
===========================================
  Files          624      624              
  Lines        28881    28881              
===========================================
- Hits         13367    13090     -277     
- Misses       15514    15791     +277

Impacted Files	Coverage Δ
Rocket.Chat/Views/Base/BaseNavigationBar.swift	0% <0%> (-100%)	⬇️
Rocket.Chat/Views/Chat/ChatAnnouncementView.swift	0% <0%> (-83.34%)	⬇️
...ontrollers/Chat/MessagesViewControllerTyping.swift	0% <0%> (-77.78%)	⬇️
...ntrollers/Chat/MessagesViewControllerJoining.swift	0% <0%> (-71.74%)	⬇️
...trollers/Chat/MessagesViewControllerDrafting.swift	20% <0%> (-60%)	⬇️
...Views/Cells/Subscription/ChatPreviewModeView.swift	0% <0%> (-43.75%)	⬇️
...Chat/Controllers/Chat/MessagesViewController.swift	1.38% <0%> (-42.86%)	⬇️
...ocket.Chat/Extensions/Models/ObjectExtension.swift	80% <0%> (-20%)	⬇️
...Chat/Models/Mapping/LoginServiceModelMapping.swift	51.68% <0%> (-14.61%)	⬇️
Rocket.Chat/Theme/ThemeableViews.swift	35.19% <0%> (-10.2%)	⬇️
... and 12 more

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