Remove Travis CI configuration

All Travis coverage (Rails matrix, Oracle 11g setup, account
provisioning) is now handled by GitHub Actions: test_gemfiles.yml
provides the Rails matrix, and test.yml / test_11g.yml cover modern
Ruby against the root Gemfile. Drop .travis.yml, the .travis/ helper
scripts, and the corresponding s.files entries in the gemspec.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: yahonda

.travis.yml

@@ -23,10 +23,6 @@ Gem::Specification.new do |s|
     ".codeclimate.yml",
     ".github/stale.yml",
     ".rubocop.yml",
-    ".travis.yml",
-    ".travis/oracle/download.sh",
-    ".travis/oracle/install.sh",
-    ".travis/setup_accounts.sh",
     "Gemfile",
     "History.txt",
     "License.txt",