Standardize capitalization of Runner in docs
Problem to solve
In both the UI and the documentation, we are inconsistent in the capitalization of the term "runner" as well as "shared runner," "group runner," and "specific runner."
We recently updated the style guide to lean toward lowercase. https://docs.gitlab.com/ee/development/documentation/styleguide.html#feature-names
Here is proposed usage for these terms.
|GitLab Runner||Capitalize only when talking about the installed software. For example: Install GitLab Runner on Linux. Do not use the plural "GitLab Runners."|
|runner||Use lowercase any other time you're talking about runners. For example: Start the runner. Update the runner. Use the runner to execute the job in your pipeline.|
|runners||Use lowercase. For example: View the list of runners.|
|shared runner||Use lowercase. Plural is fine too. For example: Enable a shared runner. View shared runners.|
|group runner||Use lowercase. Plural is fine too. For example: Enable a group runner. View group runners.|
|specific runner||User lowercase. Plural is fine too. For example: Enable a specific runner. View specific runners.|