fix line breaks in vignette

vignettes/umap.Rmd

@@ -88,13 +88,13 @@ set.seed(123456)
 Uniform Manifold Approximation and Projection (UMAP) is an algorithm for
 dimensional reduction. Its details are described by [McInnes, Healy, and
 Melville](https://arxiv.org/abs/1802.03426) and its official implementation
-is available through a python package [umap-learn](https://github.
-com/lmcinnes/umap). The R package `umap` described in this vignette is a
-separate work that provides two implementations for using UMAP within the R
-environment. One implementation is written from-scratch and another links to
-the official umap-learn. (Another R package,
-[uwot](https://CRAN.R-project.org/package=uwot), provides a separate
-implementation with a slightly different interface).
+is available through a python package
+[umap-learn](https://github.com/lmcinnes/umap). The R package `umap`
+described in this vignette is a separate work that provides two
+implementations for using UMAP within the R environment. One implementation
+is written from-scratch and another links to the official umap-learn.
+(Another R package, [uwot](https://CRAN.R-project.org/package=uwot),
+provides a separate implementation with a slightly different interface).
 
 The vignette covers basic usage, tuning, stability and reproducibility, and
 discusses toggling between different implementations. Throughout, the