chore: revert ci changes (#1425)

## What this PR does / why we need it:

The required_checks must contain `ci`, and because of the recent changes
the `ci` check is not running anymore for PRs that only update the
`VERSION`. This PR reverts the GHA changes to unblock the release.

This reverts commit e0fd082.

## Which issue(s) this PR fixes:

## Special notes for your reviewer:

## Does this PR introduce a user-facing change?
```
No.
```

.github/workflows/ci.yml

@@ -4,9 +4,6 @@
 name: ci
 on:
   pull_request:
-    paths-ignore:
-      - '*.md'
-      - 'VERSION'
 
 jobs:
   checks:

makefiles/unix.mk

@@ -51,11 +51,6 @@ test/ci: build
 mod/check:
 	@./hack/mod-check
 
-## check if VERSION file contains a valid semantic version
-.PHONY: version/check
-version/check:
-	@./hack/version-check
-
 ## creates a new release tag
 .PHONY: release/tag
 release/tag: VERSION?=v$(shell cat VERSION)