Bump nginx from 1.21.3 to 1.21.4

This changes the base image to Debian Bullseye, which means that
one dependency was needed to be updated.

Author: JonasAlfredsson

docs/dockerhub_tags.md

@@ -17,7 +17,8 @@ are updated.
 
 | Major | Minor | Patch | Nginx              |
 | ----: | ----: | ----: | :----------------- |
-| 3     | 3.0   | 3.0.1 | 3.0.1-nginx1.21.3  |
+| 3     | 3.0   | 3.0.1 | 3.0.1-nginx1.21.4  |
+|       |       |       | 3.0.1-nginx1.21.3  |
 |       |       | 3.0.0 | 3.0.0-nginx1.21.3  |
 | 2     | 2.4   | 2.4.1 | 2.4.1-nginx1.21.3  |
 |       |       |       | 2.4.1-nginx1.21.1  |

src/Dockerfile

@@ -1,4 +1,4 @@
-FROM nginx:1.21.3
+FROM nginx:1.21.4
 LABEL maintainer="Jonas Alfredsson <jonas.alfredsson@protonmail.com>"
 
 ENV CERTBOT_DNS_AUTHENTICATORS \
@@ -25,7 +25,7 @@ RUN set -ex && \
             build-essential \
             cargo \
             curl \
-            libffi6 \
+            libffi7 \
             libffi-dev \
             libssl-dev \
             openssl \

src/Dockerfile-alpine

@@ -1,4 +1,4 @@
-FROM nginx:1.21.3-alpine
+FROM nginx:1.21.4-alpine
 LABEL maintainer="Jonas Alfredsson <jonas.alfredsson@protonmail.com>"
 
 ENV CERTBOT_DNS_AUTHENTICATORS \