databases/pg_search: fix build

The distfile tarball mecab-ipadic-2.7.0-20070801.tar.gz was re-rolled.
Their file contents are identical, but metadata was changed.

Example:

--rw-r--r-- 0 1000 1000 61 Jun 10 2007 mecab-ipadic-2.7.0-20070801/README
+-rw-rw-r-- 0 root root 61 Feb 23 2024 mecab-ipadic-2.7.0-20070801/README