math/ruby-spreadsheet: update to 1.2.5

Update math/ruby-spreadsheet to 1.2.5.

### 1.2.5 23.10.2019
Author: Jesu��s Manuel Garci��a Mun��oz <jesus@bebanjo.com>
Date:   Wed Oct 23 20:26:01 2019 +0200

* Fixes unrecognized date format

### 1.2.4 24.05.2019
Author: Cyril Champier <cyril.champier@doctolib.com>
Date:   Fri May 24 12:56:52 2019 +0200

* correct ruby version check
* can read frozen string io

### 1.2.3 12.03.2019
Author: taichi <taichi730@gmail.com>
Date:   Tue Mar 12 22:29:12 2019 +0900

* Remove workaround for ruby-ole gem

### 1.2.2 01.03.2019
Author: taichi <taichi730@gmail.com>
Date:   Fri Mar 1 13:00:28 2019 +0900

* fixed unit test errors caused by frozen-string-literal
* removed ruby 2.3.8 with frozen-string-literal from CI regression
  (It seems that standard libraries for this version does not support the
  feature enough.)
* enable '--enable-frozen-string-literal' option on CI test

### 1.2.1 28.2.2019
Author: taichi <taichi730@gmail.com>
Date:   Thu Feb 28 10:30:46 2019 +0900

* Merge pull request #231 from taichi-ishitani/separated_version_file
* Merge pull request #230 from taichi-ishitani/frozen_string_literal_support


(taca)