update nushell's str collect command to str join (#2532)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: fdncred

docs/changelog/2532.bugfix.rst

@@ -0,0 +1,2 @@
+The nushell command 'str collect' has been superseded by the 'str join' command. The activate.nu script has
+been updated to reflect this change.

src/virtualenv/activation/nushell/activate.nu

@@ -62,7 +62,7 @@ export-env {
     )
 
     let venv_path = ([$virtual_env $bin] | path join)
-    let new_path = ($old_path | prepend $venv_path | str collect $path_sep)
+    let new_path = ($old_path | prepend $venv_path | str join $path_sep)
 
     let new_env = {
         $path_name  : $new_path
@@ -102,7 +102,7 @@ export-env {
       })
 
       $new_env | merge {
-        _OLD_VIRTUAL_PATH   : ($old_path | str collect $path_sep)
+        _OLD_VIRTUAL_PATH   : ($old_path | str join $path_sep)
         _OLD_PROMPT_COMMAND : $old_prompt_command
         PROMPT_COMMAND      : $new_prompt
         VIRTUAL_PROMPT      : $virtual_prompt