fix the pretty printing of failing tests in std (#10373)

related to
-
https://github.com/nushell/nushell/pull/10293/files#diff-371ea1a6b13ef0f2f10ddd0b23b86c54eb8221892e45c2e4c1913a233c585ae7R137

# Description
looks to me like https://github.com/nushell/nushell/pull/10293
introduced the use of `map` command in `std testing`, but it's not a
valid Nushell command, right?

this PR uses `each` as a replacement, that's what the error even says

crates/nu-std/std/testing.nu

@@ -134,7 +134,7 @@ def show-pretty-test [indent: int = 4] {
     let test = $in
 
     [
-        (1..$indent | map {" "} | str join)
+        (1..$indent | each {" "} | str join)
         (match $test.result {
             "pass" => { ansi green },
             "skip" => { ansi yellow },