fix(mdatagen): correct import order in package_test.go template

Fix import grouping to properly separate standard library imports from
third-party imports. This resolves the goimpi check failure in CI.

Signed-off-by: SACHIN <[email protected]>

Author: SACHIN

cmd/mdatagen/internal/templates/package_test.go.tmpl

@@ -7,8 +7,8 @@ import (
     "os"
     {{- end }}
 	"testing"
-
     {{- if not .Tests.GoLeak.Skip }}
+
     "go.uber.org/goleak"
     {{- end }}
 )