Bump bottle from 0.12.8 to 0.12.19 in /demo-bottle

Bumps [bottle](https://github.com/bottlepy/bottle) from 0.12.8 to 0.12.19.
- [Release notes](https://github.com/bottlepy/bottle/releases)
- [Changelog](https://github.com/bottlepy/bottle/blob/master/docs/changelog.rst)
- [Commits](bottlepy/bottle@0.12.8...0.12.19)

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

Author: dependabot[bot]

demo-bottle/requirements.txt

@@ -1,4 +1,4 @@
-bottle==0.12.8
+bottle==0.12.19
 beaker==1.6.4
 paste==1.7.5.1
 jinja2==2.7.3