docs: Prepare for new sub tree

See #11925

docs/content/en/functions/lang/FormatNumber.md

@@ -1,21 +0,0 @@
----
-title: lang.FormatNumber
-description: Returns a numeric representation of a number with the given precision for the current language and region.
-categories: []
-keywords: []
-action:
-  aliases: []
-  related:
-    - functions/lang/FormatAccounting
-    - functions/lang/FormatCurrency
-    - functions/lang/FormatNumberCustom
-    - functions/lang/FormatPercent
-  returnType: string
-  signatures: [lang.FormatNumber PRECISION NUMBER]
----
-
-```go-html-template
-{{ 512.5032 | lang.FormatNumber 2 }} → 512.50
-```
-
-{{% include "functions/_common/locales.md" %}}