docs/builder: fix typo
@@ -2043,7 +2043,7 @@ RUN echo hello
If you specify `--build-arg CONT_IMG_VER=<value>` on the command line, in both
cases, the specification on line 2 does not cause a cache miss; line 3 does
cause a cache miss.`ARG CONT_IMG_VER` causes the RUN line to be identified
-as the same as running `CONT_IMG_VER=<value>` echo hello, so if the `<value>`
+as the same as running `CONT_IMG_VER=<value> echo hello`, so if the `<value>`
changes, we get a cache miss.
Consider another example under the same command line:
