[6.0] Deprecated lang strings

[brianteeman]

Found three additional files with strings marked as to be removed in 6

code review

[Quy]

I have tested this item ✅ successfully on a78a41d

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[Kostelano]

At least these more lines:

COM_FIELDS_FIELD_FORM_LAYOUT_LABEL

COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_TESTING
INSTL_MB_STRING_OVERLOAD_OFF
INSTL_NOTICEMBSTRINGOVERLOAD

JGLOBAL_WARNIE

JLIB_INSTALLER_ERROR_PACK_UNINSTALL_UNKNOWN_EXTENSION

MOD_USER_DARK_MODE
MOD_USER_LIGHT_MODE

PLG_CODEMIRROR_FIELDSET_APPEARANCE_OPTIONS_LABEL (..etc. There is a whole block of lines here)

PLG_FIELDS_LIST_PARAMS_FORM_LAYOUT_FANCY_SELECT

PLG_FIELDS_SQL_PARAMS_FORM_LAYOUT_FANCY_SELECT

INSTL_MB_STRING_OVERLOAD_OFF (In the installation file)
INSTL_NOTICE_MBSTRING_OVERLOAD_OFF (In the installation file)

[brianteeman]

@Kostelano thanks - added those

[Kostelano]

I have tested this item ✅ successfully on 4f131d8

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[tecpromotion]

I have tested this item ✅ successfully on 4f131d8

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/44103.}

[tecpromotion]

Thanks @brianteeman

[richard67]

RTC

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[softforge]

Thank you for all your work on this PR