Complete keystore CLI options documentation (elastic#54242)

The documentation was missing the long option for the force option, and
the short option for the stdin option. This commit addresses this by
adding these to the documentation.

docs/reference/commands/keystore.asciidoc

@@ -52,7 +52,7 @@ two confirmation prompts, use the `-f` parameter.
 
 `create`:: Creates the keystore.
 
-`-f`:: When used with the `add` parameter, the command no longer prompts you
+`-f, --force`:: When used with the `add` parameter, the command no longer prompts you
 before overwriting existing entries in the keystore. Also, if you haven't
 created a keystore yet, it creates a keystore that is obfuscated but not
 password protected.
@@ -76,7 +76,7 @@ names can be specified as arguments to the `add` command.
 
 `-s, --silent`:: Shows minimal output.
 
-`--stdin`:: When used with the `add` parameter, you can pass the settings values
+`-x, --stdin`:: When used with the `add` parameter, you can pass the settings values
 through standard input (stdin). Separate multiple values with carriage returns
 or newlines. See <<add-string-to-keystore>>.