fix(scripts): unset CODER_URL and CODER_SESSION_TOKEN for development server (#19620)

The coder-login module was recently updated to set environment variables
instead of running `coder login`.

This unfortunately broke `develop.sh`:

```
Encountered an error running "coder login", see "coder login --help" for more information
error: Trace=[create api key: ]
```

Unsetting these env vars so that they do not interfere.

scripts/develop.sh

@@ -21,6 +21,11 @@ password="${CODER_DEV_ADMIN_PASSWORD:-${DEFAULT_PASSWORD}}"
 use_proxy=0
 multi_org=0
 
+# Ensure that extant environment variables do not override
+# the config dir we use to override auth for dev.coder.com.
+unset CODER_SESSION_TOKEN
+unset CODER_URL
+
 args="$(getopt -o "" -l access-url:,use-proxy,agpl,debug,password:,multi-organization -- "$@")"
 eval set -- "$args"
 while true; do