docs: update dockerfiles for v0.9.0 (#801)

* docs: update dockerfiles for v0.9.0

* docs: use latest tag for docker files

docs/configuration/examples/docker/autocert.docker-compose.yml

@@ -1,7 +1,7 @@
 version: "3"
 services:
   pomerium:
-    image: pomerium/pomerium:v0.8.0
+    image: pomerium/pomerium:latest
     environment:
       # Generate new secret keys. e.g. `head -c32 /dev/urandom | base64`
       - COOKIE_SECRET=V2JBZk0zWGtsL29UcFUvWjVDWWQ2UHExNXJ0b2VhcDI=

docs/configuration/examples/docker/basic.docker-compose.yml

@@ -1,7 +1,7 @@
 version: "3"
 services:
   pomerium:
-    image: pomerium/pomerium:v0.8.0
+    image: pomerium/pomerium:latest
     environment:
       # Generate new secret keys. e.g. `head -c32 /dev/urandom | base64`
       - COOKIE_SECRET=V2JBZk0zWGtsL29UcFUvWjVDWWQ2UHExNXJ0b2VhcDI=

docs/configuration/examples/docker/nginx.docker-compose.yml

@@ -12,7 +12,7 @@ services:
       - /var/run/docker.sock:/tmp/docker.sock:ro
 
   pomerium-authenticate:
-    image: pomerium/pomerium:v0.8.0 # or `build: .` to build from source
+    image: pomerium/pomerium:latest # or `build: .` to build from source
     restart: always
     environment:
       - SERVICES=authenticate
@@ -39,7 +39,7 @@ services:
       - 443
 
   pomerium-proxy:
-    image: pomerium/pomerium:v0.8.0 # or `build: .` to build from source
+    image: pomerium/pomerium:latest # or `build: .` to build from source
     restart: always
     environment:
       - SERVICES=proxy
@@ -61,7 +61,7 @@ services:
       - 443
 
   pomerium-authorize:
-    image: pomerium/pomerium:v0.8.0 # or `build: .` to build from source
+    image: pomerium/pomerium:latest # or `build: .` to build from source
     restart: always
     environment:
       - SERVICES=authorize
@@ -77,7 +77,7 @@ services:
       - 443
 
   pomerium-cache:
-    image: pomerium/pomerium:v0.8.0 # or `build: .` to build from source
+    image: pomerium/pomerium:latest # or `build: .` to build from source
     restart: always
     environment:
       - SERVICES=cache