sample/trick2018/03-tompng: merge upstream fixes

* Remove `ruby '2.5.0'`
* Add `source 'https://rubygems.org'`
* Avoid `Kernel#Integer`

Thanks to tompng.  Fixes #14930.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65123 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

sample/trick2018/03-tompng/Gemfile

@@ -1,2 +1,2 @@
-ruby '2.5.0'
+source 'https://rubygems.org'
 gem 'chunky_png'

sample/trick2018/03-tompng/Gemfile.lock

@@ -1,4 +1,5 @@
 GEM
+  remote: https://rubygems.org/
   specs:
     chunky_png (1.3.8)
 
@@ -8,8 +9,5 @@ PLATFORMS
 DEPENDENCIES
   chunky_png
 
-RUBY VERSION
-   ruby 2.5.0p0
-
 BUNDLED WITH
    1.16.1

sample/trick2018/03-tompng/entry.rb

@@ -1,7 +1,7 @@
 X=[];class String def-@;replace ?-+self end;def-a;X.reject!{|x|x.
 __id__==__id__};a.replace(self+?-+a) end end;at_exit{eval C=(Zlib
-.inflate Integer((X*?-).tr(?-,'').tr('q-z','0-9'),26).digits(256)
-.pack'C*')};def method_missing n;(X<<n.to_s)[-1]end;require'zlib'
+.inflate((X*?-).tr(?-,'').tr('q-z','0-9').to_i(26).digits(0x100).
+pack'C*'))};def method_missing n;(X<<n.to_s)[-1]end;require'zlib'
 fzygtoxyzgntmdmuwvfoffbpmvzojpkhczvjvjdbtscnldwbdoprackddovivvmkz
 ponzmosvtjciwkgaslscxxxwudeesmmqpfhislxuxnnypulxstzgobyaekqqhbjcg
 mvko------------ddkeys----eivhnccaqyiw---bzyccmt-----------ymtnge