Remove Old Plugin Files

Why these changes are being introduced:
There is no need to keep the old files!

How this addresses that need:
* Update the Makefile to remove the stage-related commands
* Minor tweak to documentation
* Remove all the old plugin source files that are no longer needed

Side effects of this change:
None.

Relevant ticket(s):
* https://mitlibraries.atlassian.net/browse/INFRA-569
* https://mitlibraries.atlassian.net/browse/INFRA-588

Author: cabutlermit

Makefile

@@ -24,29 +24,3 @@ publish-dev: dist-dev ## Build, tag and push (intended for developer-based manua
 	docker login -u AWS -p $$(aws ecr get-login-password --region us-east-1) $(ECR_URL_DEV)
 	docker push $(ECR_URL_DEV):latest
 	docker push $(ECR_URL_DEV):`git describe --always`
-
-### If this is a Lambda repo, uncomment the two lines below     ###
-# update-lambda-dev: ## Updates the lambda with whatever is the most recent image in the ecr (intended for developer-based manual update)
-#	aws lambda update-function-code --function-name $(FUNCTION_DEV) --image-uri $(ECR_URL_DEV):latest
-
-
-### Terraform-generated manual shortcuts for deploying to Stage. This requires  ###
-###   that ECR_NAME_STAGE, ECR_URL_STAGE, and FUNCTION_STAGE environment        ###
-###   variables are set locally by the developer and that the developer has     ###
-###   authenticated to the correct AWS Account. The values for the environment  ###
-###   variables can be found in the stage_build.yml caller workflow.            ###
-dist-stage: ## Only use in an emergency
-	docker build \
-		--platform linux/amd64 \
-	    -t $(ECR_URL_STAGE):latest \
-		-t $(ECR_URL_STAGE):`git describe --always` \
-		-t $(ECR_NAME_STAGE):latest .
-
-publish-stage: ## Only use in an emergency
-	docker login -u AWS -p $$(aws ecr get-login-password --region us-east-1) $(ECR_URL_STAGE)
-	docker push $(ECR_URL_STAGE):latest
-	docker push $(ECR_URL_STAGE):`git describe --always`
-
-### If this is a Lambda repo, uncomment the two lines below     ###
-# update-lambda-stage: ## Updates the lambda with whatever is the most recent image in the ecr (intended for developer-based manual update)
-#	aws lambda update-function-code --function-name $(FUNCTION_STAGE) --image-uri $(ECR_URL_STAGE):latest

docs/HowTos/HOWTO-premium-plugins.md

@@ -36,7 +36,7 @@ Before installing the license key, the *Marketplace* plugin must be activated. T
 According to the support team at Matomo, the premium license key can be installed in two instances of Matomo, "stage" and "prod." So, we can do some initial validation of a license key in Dev1, but the key cannot remain installed in the Dev1 instance. The license key installation can either be done by a user with "superuser" privileges in the Matomo web UI or it can be done by a member of InfraEng who has ssh access to the running container task/service. The CLI command is
 
 ```bash
-./console marketplace:set-license-key --license-key=LICENSE-KEY "<key>"
+./console marketplace:set-license-key --license-key=<license_key>
 ```
 
 This needs to be done once on each of the stage & prod instances of Matomo.