chore: address adr-gen feedback (#1632)

Addresses
celestiaorg/celestia-app#1599 (review)

## Testing

```shell
$ make adr-gen

$ git status
On branch rp/adr-gen
Your branch is up to date with 'origin/rp/adr-gen'.

Untracked files:
  (use "git add <file>..." to include in what will be committed)
	docs/architecture/adr-template.md
```

Makefile

@@ -128,8 +128,8 @@ test-cover:
 	@export VERSION=$(VERSION); bash -x scripts/test_cover.sh
 .PHONY: test-cover
 
-## adr-gen: Download the ADR template from the celestiaorg/.github repo. Ex. `make adr-gen NUM=016 TITLE=my-adr-title`
+## adr-gen: Download the ADR template from the celestiaorg/.github repo. Ex. `make adr-gen`
 adr-gen:
-	@echo "--> Generating ADR template"
-	@curl -sSL https://raw.githubusercontent.com/celestiaorg/.github/main/adr-template.md > docs/architecture/adr-$(NUM)-$(TITLE).md
+	@echo "--> Downloading ADR template"
+	@curl -sSL https://raw.githubusercontent.com/celestiaorg/.github/main/adr-template.md > docs/architecture/adr-template.md
 .PHONY: adr-gen