Remove requirement on mathn

The test using mathn was first introduced in f1d9179 to check that the
`distance_of_time_in_words` properly doesn't use the `Fixnum#/` method
by explicitly requiring this library as it redefines this method.

Given that `mathn` has been gemified in Ruby 2.5 and is deprecated since
version 2.2, we can certainly safely assume that people will most-likely
not require this library in their application.

However, to make sure that we don't regress, let's add a test similar to
the one before f1d9179.

1 files changed, 0 insertions, 4 deletions

diff --git a/Gemfile b/Gemfile
index 7f33a1226f..df25abe65b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -154,7 +154,3 @@ end
 gem "ibm_db" if ENV["IBM_DB"]
 gem "tzinfo-data", platforms: [:mingw, :mswin, :x64_mingw, :jruby]
 gem "wdm", ">= 0.1.0", platforms: [:mingw, :mswin, :x64_mingw, :mswin64]
-
-platforms :ruby_25 do
-  gem "mathn"
-end