Change the Ruby version from 2.4.4 to 2.6.6 in README (#8557)

README.md

@@ -96,7 +96,7 @@ For installation, prerequisites include sqlite3 and rvm. [Click here for a compl
 3. Enter the new **plots2** directory with `cd plots2`.
 4. Set the upstream remote to the original repository url so that git knows where to fetch updates from in future: `git remote add upstream https://github.com/publiclab/plots2.git`
 5. Steps to install gems:
-    * You may need to first run `bundle install` if you have older gems in your environment from previous Rails work. If you get an error message like `Your Ruby version is 2.x.x, but your Gemfile specified 2.4.4` then you need to install the ruby version 2.6.6 using `rvm` or `rbenv`.
+    * You may need to first run `bundle install` if you have older gems in your environment from previous Rails work. If you get an error message like `Your Ruby version is 2.x.x, but your Gemfile specified 2.6.6` then you need to install the ruby version 2.6.6 using `rvm` or `rbenv`.
 	    * Using **rvm**: `rvm install 2.6.6` followed by `rvm use 2.6.6`
 	    * Using **rbenv**:  `rbenv install 2.6.6` followed by `rbenv local 2.6.6`
     * Install gems with `bundle install --without production mysql` from the rails root folder, to install the gems you'll need, excluding those needed only in production.