update go to go1.20.4

go1.20.4 (released 2023-05-02) includes three security fixes to the html/template
package, as well as bug fixes to the compiler, the runtime, and the crypto/subtle,
crypto/tls, net/http, and syscall packages. See the Go 1.20.4 milestone on our
issue tracker for details:

https://github.com/golang/go/issues?q=milestone%3AGo1.20.4+label%3ACherryPickApproved

release notes: https://go.dev/doc/devel/release#go1.20.4
full diff: https://github.com/golang/go/compare/go1.20.3...go1.20.4

from the announcement:

> These minor releases include 3 security fixes following the security policy:
>
> - html/template: improper sanitization of CSS values
>
>   Angle brackets (`<>`) were not considered dangerous characters when inserted
>   into CSS contexts. Templates containing multiple actions separated by a '/'
>   character could result in unexpectedly closing the CSS context and allowing
>   for injection of unexpected HMTL, if executed with untrusted input.
>
>   Thanks to Juho Nurminen of Mattermost for reporting this issue.
>
>   This is CVE-2023-24539 and Go issue https://go.dev/issue/59720.
>
> - html/template: improper handling of JavaScript whitespace
>
>   Not all valid JavaScript whitespace characters were considered to be
>   whitespace. Templates containing whitespace characters outside of the character
>   set "\t\n\f\r\u0020\u2028\u2029" in JavaScript contexts that also contain
>   actions may not be properly sanitized during execution.
>
>   Thanks to Juho Nurminen of Mattermost for reporting this issue.
>
>   This is CVE-2023-24540 and Go issue https://go.dev/issue/59721.
>
> - html/template: improper handling of empty HTML attributes
>
>   Templates containing actions in unquoted HTML attributes (e.g. "attr={{.}}")
>   executed with empty input could result in output that would have unexpected
>   results when parsed due to HTML normalization rules. This may allow injection
>   of arbitrary attributes into tags.
>
>   Thanks to Juho Nurminen of Mattermost for reporting this issue.
>
>   This is CVE-2023-29400 and Go issue https://go.dev/issue/59722.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Dockerfile

@@ -15,7 +15,7 @@
 #   See the License for the specific language governing permissions and
 #   limitations under the License.
 
-ARG GO_VERSION=1.20.3
+ARG GO_VERSION=1.20.4
 ARG XX_VERSION=1.2.1
 ARG GOLANGCI_LINT_VERSION=v1.52.2
 ARG ADDLICENSE_VERSION=v1.0.0