translations: use a more distinctive separator

I found that the translator would sometimes replace the pipe character
with another symbol (maybe it got confused thinking the character is
part of the text?).

Added spaces around the pipe to make it more clear that it's definitely
the separator.

beetsplug/lyrics.py

@@ -744,6 +744,7 @@ class Google(SearchBackend):
 class Translator(RequestHandler):
     TRANSLATE_URL = "https://api.cognitive.microsofttranslator.com/translate"
     LINE_PARTS_RE = re.compile(r"^(\[\d\d:\d\d.\d\d\]|) *(.*)$")
+    SEPARATOR = " | "
     remove_translations = partial(re.compile(r" / [^\n]+").sub, "")
 
     _log: Logger
@@ -773,14 +774,16 @@ class Translator(RequestHandler):
         map the translations back to the original texts.
         """
         unique_texts = list(dict.fromkeys(texts))
+        text = self.SEPARATOR.join(unique_texts)
         data: list[TranslatorAPI.Response] = self.post_json(
             self.TRANSLATE_URL,
             headers={"Ocp-Apim-Subscription-Key": self.api_key},
-            json=[{"text": "|".join(unique_texts)}],
+            json=[{"text": text}],
             params={"api-version": "3.0", "to": self.to_language},
         )
 
-        translations = data[0]["translations"][0]["text"].split("|")
+        translated_text = data[0]["translations"][0]["text"]
+        translations = translated_text.split(self.SEPARATOR)
         trans_by_text = dict(zip(unique_texts, translations))
         return list(zip(texts, (trans_by_text.get(t, "") for t in texts)))