Sections named header are centered in html_vignette

[EmilHvitfeldt]

Found this peculiar thing where when using html_vignette if you name a section "header" it will center it along with the section context. This will only be the case for the first section named header.

---
title: "test"
output: rmarkdown::html_vignette
---

## This is a title

This is normal text.

## header

This is also normal text.

## New header

and this is also text.

## header

and this is also text.

## New header

and this is also text.

R version 3.6.0 (2019-04-26)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS Mojave 10.14.6, RStudio 1.2.1522

Locale: en_US.UTF-8 / en_US.UTF-8 / en_US.UTF-8 / C / en_US.UTF-8 / en_US.UTF-8

Package version:
  base64enc_0.1.3    digest_0.6.23      evaluate_0.14      glue_1.3.1        
  graphics_3.6.0     grDevices_3.6.0    highr_0.8          htmltools_0.4.0   
  jsonlite_1.6       knitr_1.26.1       magrittr_1.5       markdown_1.1      
  methods_3.6.0      mime_0.7           Rcpp_1.0.3         rlang_0.4.2.9000  
  rmarkdown_2.0      stats_3.6.0        stringi_1.4.3      stringr_1.4.0.9000
  tinytex_0.18       tools_3.6.0        utils_3.6.0        xfun_0.11         
  yaml_2.2.0        

Pandoc version: 2.5

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[yihui]

Should be fixed now. Thanks for the report!

[github-actions]

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