fix parse_si for Japanese excel files

 Hi.

using #parse_si 'Phonetic Properties' items for Japanese excel files,
the Phonetic items(KATAKANA) represents pronunciation hints of String(KANJI).

```
<si>
 <t>漢字(japanese KANJI)</t>
 <rPh>
  <t>フリガナ(this is KATAKANA for pronounciation:漢字)</t>
 </rPh>
</si>
```

It expected get '漢字' . but got '漢字フリガナ'.
so replace these string, because this can be caused by only `<rPh>`.