test(shell): remove shallow PowerShell guard assertion

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: JanDeDobbeleer

src/shell/pwsh_test.go

@@ -33,11 +33,6 @@ Enable-PoshVIMode`
 	assert.Equal(t, want, got)
 }
 
-func TestPwshStreamingGuard(t *testing.T) {
-	assert.Contains(t, pwshInit, "if (Test-Path Env:POSH_DISABLE_STREAMING) {")
-	assert.Contains(t, pwshInit, "return")
-}
-
 func TestSourceCommandAsyncPwsh(t *testing.T) {
 	got := sourceCommandAsync(PWSH, "C:/cache/init.pwsh.ps1")