fix(md prompter): accessible prompt allows blank

Allow the accessible markdownEditor prompt to be blank when the blank
comes from the result of an interactive session with an editor, even when
blankAllowed is false.

This behavior aligns the accessible prompter with the behavior of the
current standard prompter.

internal/prompter/prompter.go

@@ -253,11 +253,6 @@ func (p *huhPrompter) MarkdownEditor(prompt, defaultValue string, blankAllowed b
 		return "", err
 	}
 
-	// TODO: blank not allowed
-	if !blankAllowed && defaultValue == "" {
-		panic("blank not allowed and no default value")
-	}
-
 	return text, nil
 }