[6.x] Move mustache typings to devDependencies (#24165)

[weltenwort]

Backports the following commits to 6.x:

• Move mustache typings to devDependencies (Move mustache typings to devDependencies #24165)

[elasticmachine]

💔 Build Failed

• continuous-integration/kibana-ci/pull-request

[weltenwort]

00:31:01.512              └- ✖ fail: "dashboard app using current data dashboard data-shared attributes data-shared-item title should update a saved search when using a custom panel title"
00:31:01.512              │      retry.try timeout: Error: retry.try timeout: Error: retry.try timeout: [POST http://localhost:9515/session/69caa62e37a9e0c57e171590926ed03e/element / {"using":"css selector","value":"[data-test-subj~=\"customDashboardPanelTitleInput\"]"}] no such element: Unable to locate element: {"method":"css selector","selector":"[data-test-subj~="customDashboardPanelTitleInput"]"}
00:31:01.515              │   (Session info: chrome=70.0.3538.67)
00:31:01.515              │   (Driver info: chromedriver=2.42.591071 (0b695ff80972cc1a65a5cd643186d2ae582cd4ac),platform=Linux 3.10.0-862.14.4.el7.x86_64 x86_64)

maybe flakey dashboard test... jenkins, test this again

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request