Fix grammar

docker/README.md

@@ -5,7 +5,7 @@
 * `latest` — the stable `master` branch [![GitHub last commit (branch)](https://img.shields.io/github/last-commit/sagemath/sage/master.svg)](https://github.com/sagemath/sage/commits/master) [![GitLab CI](https://gitlab.com/sagemath/sage/badges/master/pipeline.svg)](https://gitlab.com/sagemath/sage/commits/master)
 * `x.x` — all stable releases of Sage are tagged with their version number.
 * `x.x.{beta,rc}x` - betas and release candidates of Sage as [tagged in our git repository](https://github.com/sagemath/sage/tags); since docker images are built and uploaded manually at the moment, there are often no recent betas here anymore.
-* `develop` — the current development version of Sage which gets merged into the `master` branch when a new version of Sage is released [![GitHub last commit (branch)](https://img.shields.io/github/last-commit/sagemath/sage/develop.svg)](https://github.com/sagemath/sage/commits/develop) [![GitLab CI](https://gitlab.com/sagemath/sage/badges/develop/pipeline.svg)](https://gitlab.com/sagemath/sage/commits/develop); again, there is often no recent develop built here anymore.
+* `develop` — the current development version of Sage which gets merged into the `master` branch when a new version of Sage is released [![GitHub last commit (branch)](https://img.shields.io/github/last-commit/sagemath/sage/develop.svg)](https://github.com/sagemath/sage/commits/develop) [![GitLab CI](https://gitlab.com/sagemath/sage/badges/develop/pipeline.svg)](https://gitlab.com/sagemath/sage/commits/develop); again, there is often no recent develop build here anymore.
 * `-py3` - until Sage 9.1, we provided Python 2 builds (with no suffix) and Python 3 builds (with the `-py3` suffix). From Sage 9.2.beta0 on, all images we provide are based on Python 3 and the `-py3` suffix survives only for historical reasons: with or without it, you get Python 3.
 
 # What is SageMath