Make it clear that the cache TTL is in seconds.

I was a bit confused when I first read these docs what units the cache TTL is in. I expected milliseconds, and had to read the cache-manager docs to confirm.

Reference: https://www.npmjs.com/package/cache-manager

Author: mistakenot

content/techniques/caching.md

@@ -52,7 +52,7 @@ await this.cacheManager.set('key', 'value');
 
 The default expiration time of the cache is 5 seconds.
 
-You can manually specify a TTL (expiration time) for this specific key, as follows:
+You can manually specify a TTL (expiration time in seconds) for this specific key, as follows:
 
 ```typescript
 await this.cacheManager.set('key', 'value', { ttl: 1000 });