remove mention of build-string from coloring_and_theming.md (#1800)

Author: Bahex

book/coloring_and_theming.md

@@ -425,7 +425,7 @@ The Nushell prompt is configurable through these environment variables and confi
 Example: For a simple prompt one could do this. Note that `PROMPT_COMMAND` requires a `block` whereas the others require a `string`.
 
 ```nu
-$env.PROMPT_COMMAND = { build-string (date now | format date '%m/%d/%Y %I:%M:%S%.3f') ': ' (pwd | path basename) }
+$env.PROMPT_COMMAND = { $"(date now | format date '%m/%d/%Y %I:%M:%S%.3f'): (pwd | path basename)" }
 ```
 
 If you don't like the default `PROMPT_INDICATOR` you could change it like this.

de/book/coloring_and_theming.md

@@ -375,7 +375,7 @@ Der Nushell Prompt ist konfigurierbar mit diesen Umgebungsvariablen:
 Beispiel: Für einen einfachen Prompt wäre folgendes mögllich. Hinweis `PROMPT_COMMAND` benötigt einen `block` wogegen die anderen einen `string` erwarten.
 
 ```nu
-$env.PROMPT_COMMAND = { build-string (date now | format date '%m/%d/%Y %I:%M:%S%.3f') ': ' (pwd | path basename) }
+$env.PROMPT_COMMAND = { $"(date now | format date '%m/%d/%Y %I:%M:%S%.3f'): (pwd | path basename)" }
 ```
 
 Soll der standard `PROMPT_INDICATOR` geändert werden, sieht das so aus.

zh-CN/book/coloring_and_theming.md

@@ -371,7 +371,7 @@ Nushell 的提示符可以通过这些环境变量进行配置：
 例如：对于一个简单的提示，我们可以这样做。注意`PROMPT_COMMAND`需要一个`block`而其他的需要一个`string`。
 
 ```nu
-$env.PROMPT_COMMAND = { build-string (date now | format date '%m/%d/%Y %I:%M:%S%.3f') ': ' (pwd | path basename) }
+$env.PROMPT_COMMAND = { $"(date now | format date '%m/%d/%Y %I:%M:%S%.3f'): (pwd | path basename)" }
 ```
 
 如果你不喜欢默认的`PROMPT_INDICATOR`，你可以这样改变它：