Revert "add path extension func to stdlib-candidate"

This reverts commit b50215132b.

stdlib-candidate/nupm.nuon

@@ -3,6 +3,6 @@
     description: "Official candidates for Nushell standard library"
     documentation: "https://github.com/nushell/nu_scripts/blob/main/stdlib-candidate/std-rfc/README.md"
     license: "https://github.com/nushell/nu_scripts/blob/main/LICENSE"
-    version: 0.4.1
+    version: 0.4.0
     type: "module"
 }

stdlib-candidate/path/mod.nu

@@ -1,28 +0,0 @@
-# Update extension of input files.
-#
-# # Example
-# - setting path ext to `rs`
-# ```nushell
-# > "ab.txt" | path extension "rs"
-# ab.rs
-# > "ab.txt" | path extension ".rs"
-# ab.rs
-#
-# - setting a list of input path ext to `rs`
-# > ["ab.txt", "cd.exe"] | path extension "rs"
-# ╭───┬──────────╮
-# │ 0 │ ab.rs    │
-# │ 1 │ cd.rs    │
-# ╰───┴──────────╯
-# ``` 
-export def extension [
-    ext: string
-] {
-    let path_parsed = $in | path parse
-    if ($ext | str starts-with ".") {
-        $path_parsed | update extension ($ext | str substring 1..) | path join
-    } else {
-        $path_parsed | update extension $ext | path join
-    }
-}
-