Make whitespace in monokai-pro-spectrum theme one step dimmer to avoid (#3814)

the white space confusion with hyphen

Co-authored-by: Fanda Vacek <fvacek@elektroline.cz>

runtime/themes/monokai_pro_spectrum.toml

@@ -6,7 +6,7 @@
 "ui.text.focus" = { fg = "yellow", modifiers= ["bold"] }
 "ui.menu" = { fg = "base8", bg = "base3" }
 "ui.menu.selected" = { fg = "base2", bg = "yellow" }
-"ui.virtual.whitespace" = "base5"
+"ui.virtual.whitespace" = "base4"
 "ui.virtual.ruler" = { bg = "base1" }
 
 "info" = "base8"