Fix some references to Postgres to be database-agnostic. (#94)

Author: rkistner

resources/performance-and-limits.mdx

@@ -10,12 +10,12 @@ The PowerSync Cloud Enterprise plan allows for limits to be customized.
 * Number of synced buckets per user: 1,000.
    * Sync requests where this number is exceeded will fail with a hard error.
    * We have plans to increase this limit.
-* Maximum row size: 15MB
-   * This applies to both the source Postgres row, and the transformed row synced to the client.
+* Maximum row/document size: 15MB
+   * This applies to both the source row/document, and the transformed row synced to the client.
 * Number of concurrent connections per [PowerSync Service](/architecture/powersync-service) instance: Limited to 3,000 by default.
-* Replicated rows (Postgres -> PowerSync Service):
-   * Expect a peak of around 2,000-4,000 operations/second for small rows, or 5MB/second for large rows.
-   * This also applies to reprocessing sync rules or adding new tables.
+* Replicated rows/documents (Source database -> PowerSync Service):
+   * Expect a peak of around 2,000-4,000 operations/second for small rows/documents, or 5MB/second for large rows/documents.
+   * This also applies to reprocessing sync rules or adding new tables/collections.
    * Smaller transactions are processed at around 60 transactions/second.
 * Synced rows (PowerSync Service -> Client):
    * Over 1M rows per client is supported, with no hard limit.