Change alacritty template to match v0.11.0+ config

[evdunbar]

As of Alacritty release 0.11.0, the syntax for setting the color of the bar changed from being nested under search to being it's own item "footer_bar". This fix matches the current Alacritty syntax and should remove the warning popup from Alacritty when loading the old style config.

Reference:

• old config
• new config

[eylles]

thanks, just for sanity i checked repology and even debian stable is on alacritty 0.11.0