Bump ttfunk from 1.7.0 to 1.8.0

Bumps [ttfunk](https://github.com/prawnpdf/ttfunk) from 1.7.0 to 1.8.0.
- [Release notes](https://github.com/prawnpdf/ttfunk/releases)
- [Changelog](https://github.com/prawnpdf/ttfunk/blob/master/CHANGELOG.md)
- [Commits](prawnpdf/ttfunk@1.7.0...1.8.0)

---
updated-dependencies:
- dependency-name: ttfunk
  dependency-type: indirect
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -28,6 +28,7 @@ GEM
       aws-sdk-core (~> 3, >= 3.191.0)
     aws-sigv4 (1.8.0)
       aws-eventstream (~> 1, >= 1.0.2)
+    bigdecimal (3.1.6)
     console (1.23.5)
       fiber-annotation
       fiber-local
@@ -75,7 +76,8 @@ GEM
     rake (13.1.0)
     ruby-rc4 (0.1.5)
     timers (4.3.5)
-    ttfunk (1.7.0)
+    ttfunk (1.8.0)
+      bigdecimal (~> 3.1)
     typhoeus (1.4.1)
       ethon (>= 0.9.0)
     yell (2.2.2)