Change "Knitr" to "knitr" in the index.qmd file

yihui uses knitr at all times, so I think the original author should be respected.

index.qmd

@@ -91,7 +91,7 @@ Combine Jupyter notebooks with flexible options to produce production quality ou
 
 <div class="tab-pane fade" id="knitr" role="tabpanel" aria-labelledby="knitr-tab">
 
-Quarto is a multi-language, next generation version of R Markdown from Posit, with many new new features and capabilities. Like R Markdown, Quarto uses [Knitr](https://yihui.org/knitr/) to execute R code, and is therefore able to render most existing Rmd files without modification.
+Quarto is a multi-language, next generation version of R Markdown from Posit, with many new new features and capabilities. Like R Markdown, Quarto uses [knitr](https://yihui.org/knitr/) to execute R code, and is therefore able to render most existing Rmd files without modification.
 
 ::: {.grid}
 ::: {.g-col-lg-6 .g-col-12}