Update zk_login.md (MystenLabs#13684)

Without tick marks it doesn't render correctly.

## Description 

Need tick marks to prevent incorrect render.
<img width="837" alt="image"
src="https://github.com/MystenLabs/sui/assets/118224482/1826f2ed-1563-4c3a-980f-4a12204bd1f2">

Also need ticks around the variables to avoid this:
<img width="745" alt="image"
src="https://github.com/MystenLabs/sui/assets/118224482/7fa83220-e6a1-4e9a-ad1d-09fd34be6852">


## Test Plan 

Local

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

doc/src/build/zk_login.md

@@ -146,13 +146,13 @@ const randomness = generateRandomness();
 const nonce = generateNonce(ephemeralKeyPair.getPublicKey(), maxEpoch, randomness);
 ```
 
-The OAuth URL can be constructed with $CLIENT_ID, $REDIRECT_URL and $Nonce as follows:
+The OAuth URL can be constructed with `$CLIENT_ID`, `$REDIRECT_URL` and `$Nonce` as follows: 
 
 | Provider | URL |
 | ----------- | ----------- |
-| Google | https://accounts.google.com/o/oauth2/v2/auth?client_id=$CLIENT_ID&response_type=id_token&redirect_uri=$REDIRECT_URL&scope=openid&nonce=$NONCE |
-| Facebook | https://www.facebook.com/v17.0/dialog/oauth?client_id=$CLIENT_ID&redirect_uri=$REDIRECT_URL&scope=openid&nonce=$NONCE&response_type=id_token |
-| Twitch | https://id.twitch.tv/oauth2/authorize?client_id=$CLIENT_ID&force_verify=true&lang=en&login_type=login&redirect_uri=$REDIRECT_URL&response_type=id_token&scope=openid&nonce=$NONCE |
+| Google | `https://accounts.google.com/o/oauth2/v2/auth?client_id=$CLIENT_ID&response_type=id_token&redirect_uri=$REDIRECT_URL&scope=openid&nonce=$NONCE` |
+| Facebook | `https://www.facebook.com/v17.0/dialog/oauth?client_id=$CLIENT_ID&redirect_uri=$REDIRECT_URL&scope=openid&nonce=$NONCE&response_type=id_token` |
+| Twitch | `https://id.twitch.tv/oauth2/authorize?client_id=$CLIENT_ID&force_verify=true&lang=en&login_type=login&redirect_uri=$REDIRECT_URL&response_type=id_token&scope=openid&nonce=$NONCE` |
 
 ## User Salt Management