Fix diagnostic indicator background for gruvbox themes (#5540)

The diagnostic indicator background did not match the column or rows background
colour as this was context specific, and the background for the indicator was
being explicitly set.

This commit removes the explicit value for the indicators background allowing
it to adapt to the context. This is aligns it with other themes, and resolves
the issue.

runtime/themes/gruvbox.toml

@@ -33,10 +33,10 @@
 "diff.delta" = "orange1"
 "diff.minus" = "red1"
 
-"warning" = { fg = "orange1", bg = "bg1" }
+"warning" = "orange1"
-"error" = { fg = "red1", bg = "bg1" }
+"error" = "red1"
-"info" = { fg = "aqua1", bg = "bg1" }
+"info" = "aqua1"
-"hint" = { fg = "blue1", bg = "bg1" }
+"hint" = "blue1"
 
 "ui.background" = { bg = "bg0" }
 "ui.linenr" = { fg = "bg4" }

runtime/themes/gruvbox_dark_hard.toml

@@ -34,10 +34,10 @@
 "diff.delta" = "orange1"
 "diff.minus" = "red1"
 
-"warning" = { fg = "orange1", bg = "bg1" }
+"warning" = "orange1"
-"error" = { fg = "red1", bg = "bg1" }
+"error" = "red1"
-"info" = { fg = "aqua1", bg = "bg1" }
+"info" = "aqua1"
-"hint" = { fg = "blue1", bg = "bg1" }
+"hint" = "blue1"
 
 "diagnostic.error" = { underline = { style = "curl", color = "red0" } }
 "diagnostic.warning" = { underline = { style = "curl", color = "orange1" } }

runtime/themes/gruvbox_light.toml

@@ -34,10 +34,10 @@
 "diff.delta" = "orange1"
 "diff.minus" = "red1"
 
-"warning" = { fg = "orange1", bg = "bg1" }
+"warning" = "orange1"
-"error" = { fg = "red1", bg = "bg1" }
+"error" = "red1"
-"info" = { fg = "aqua1", bg = "bg1" }
+"info" = "aqua1"
-"hint" = { fg = "blue1", bg = "bg1" }
+"hint" = "blue1"
 
 "ui.background" = { bg = "bg0" }
 "ui.linenr" = { fg = "bg4" }