docs: update README backends

Removing pandas backend from the list and rephrasing count verbiage

README.md

@@ -135,7 +135,7 @@ This allows you to combine the flexibility of Python with the scale and performa
 
 ## Backends
 
-Ibis supports 20+ backends:
+Ibis supports nearly 20 backends:
 
 - [Apache DataFusion](https://ibis-project.org/backends/datafusion/)
 - [Apache Druid](https://ibis-project.org/backends/druid/)
@@ -148,7 +148,6 @@ Ibis supports 20+ backends:
 - [Exasol](https://ibis-project.org/backends/exasol)
 - [MySQL](https://ibis-project.org/backends/mysql/)
 - [Oracle](https://ibis-project.org/backends/oracle/)
-- [pandas](https://ibis-project.org/backends/pandas/)
 - [Polars](https://ibis-project.org/backends/polars/)
 - [PostgreSQL](https://ibis-project.org/backends/postgresql/)
 - [RisingWave](https://ibis-project.org/backends/risingwave/)