feat: upgrade to covidcast v1.12.9

Author: sgratzl

content/covidcast/release-log/headless/v1.12.9.md

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+---
+title: v1.12.9
+date: 2021-03-01
+---
+
+This release changes two signals with their improved version.
+
+### Signal Changes
+
+- Replaced "Vaccine Acceptance" with signal including both already received the vaccine and definitely or probably choose to get vaccinated.
+- Replaced "COVID-Related Doctor Visits" with new signal from Change Healthcare. For more details see: [`smoothed_outpatient_cli`](https://cmu-delphi.github.io/delphi-epidata/api/covidcast-signals/chng.html)
+
+### New Features
+
+- [#730](https://github.com/cmu-delphi/www-covidcast/pull/730) (re: [#729](https://github.com/cmu-delphi/www-covidcast/issues/729)) Mobile survey toc on medium devices