Docs: Better document Go dep upgrading (#34745)

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

UPGRADING_DEPENDENCIES.md

@@ -4,14 +4,14 @@ Upgrading Go or Node.js requires making changes in many different files. See bel
 
 ## Go
 
-- CircleCi
+- Drone
 - `grafana/build-container`
 - Appveyor
 - Dockerfile
 
 ## Node.js
 
-- CircleCI
+- Drone
 - `grafana/build-container`
 - Appveyor
 - Dockerfile
@@ -42,6 +42,10 @@ GO111MODULE=on go mod tidy
 
 You have to commit the changes to `go.mod` and `go.sum` before submitting the pull request.
 
+### Upgrading dependencies
+
+If you need to upgrade a direct or indirect dependency, you can do it like so, $MODULE being the dependency in question: `go get -u $MODULE`. The corresponding entry in go.mod should then have the version you specified; if it's an indirect dependency, the entry should have the `// indirect` comment. Follow this by executing `go mod tidy`, to ensure that go.mod and go.sum are up to date. If the indirect dependency turns out to not be used (transitively) by any of our packages, `go mod tidy` will actually strip it from go.mod. In that case, you can just ignore it since it isn't used in the end.
+
 ## Node.js dependencies
 
 Updated using `yarn`.
@@ -50,9 +54,9 @@ Updated using `yarn`.
 
 ## Where to make changes
 
-### CircleCI
+### Drone
 
-Our builds run on CircleCI through our build script.
+Our CI builds run on Drone.
 
 #### Files
 
@@ -66,7 +70,7 @@ Our builds run on CircleCI through our build script.
 
 ### grafana/build-container
 
-The main build step (in CircleCI) is built using a custom build container that comes pre-baked with some of the necessary dependencies.
+The main build steps (in Drone) happen using a custom Docker image that comes pre-baked with some of the necessary dependencies.
 
 Link: [grafana/build-container](https://github.com/grafana/grafana/tree/main/scripts/build/ci-build)