build(deps): bump ffi from 1.15.3 to 1.15.4

[dependabot[bot]]

Bumps ffi from 1.15.3 to 1.15.4.

Changelog

Sourced from ffi's changelog.

1.15.4 / 2021-09-01

Fixed:

• Fix build for uClibc. #913
• Correct module lookup when including ffi-module gem. #912

Changed:

• Use ruby code of the ffi gem in JRuby-9.2.20+. #915

Commits

• 7429c5a Bump VERSION to 1.15.4 and add CHANGELOG entry
• cd0db90 Merge pull request #913 from xtkoba/uclibc
• 05eac54 Fix build for uClibc
• 7c70b82 Correct module lookup when including ffi-module
• 4d8fbd9 Allow prerelease FFI::VERSION
• 111d151 Remove unused rubygems-tasks development dependency
• 50098f2 Bump VERSION to 1.15.4.pre1
• 0dbbe5e Lower the JRuby version guard to 9.2.20
• 1880a71 CI: Install libffi which matches running arch (#905)
• See full diff in compare view

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