Updated docker tagging to match correct ubuntu version (#2440)

The docker Readme seams to tag the built docker images with version 2004, but is built using version 2204. This PR simply starts tagging the images correctly to avoid confusion.

docker/README.md

@@ -21,25 +21,25 @@ docker build -t carbon-ubuntu2204-base ./ubuntu2204/base
 Build image using git repository
 
 ```bash
-docker build -t carbon-ubuntu2004 ./ubuntu2204/github
+docker build -t carbon-ubuntu2204 ./ubuntu2204/github
 ```
 
 Build image using copy instruction
 
 ```bash
-docker build -f ./ubuntu2204/Dockerfile -t carbon-ubuntu2004 ..
+docker build -f ./ubuntu2204/Dockerfile -t carbon-ubuntu2204 ..
 ```
 
 Run image
 
 ```bash
-docker run carbon-ubuntu2004
+docker run carbon-ubuntu2204
 ```
 
 Run image using specific file
 
 ```bash
-docker run carbon-ubuntu2004 bazel run //explorer -- ./explorer/testdata/print/format_only.carbon
+docker run carbon-ubuntu2204 bazel run //explorer -- ./explorer/testdata/print/format_only.carbon
 ```
 
 ### Using a mounted volume
@@ -51,5 +51,5 @@ cd ..
 ```
 
 ```bash
-docker run -w "/carbon-lang" -v "${PWD}:/carbon-lang" "carbon-ubuntu2004-base" bazel run "//explorer" -- "./explorer/testdata/print/format_only.carbon"
+docker run -w "/carbon-lang" -v "${PWD}:/carbon-lang" "carbon-ubuntu2204-base" bazel run "//explorer" -- "./explorer/testdata/print/format_only.carbon"
 ```