Update difftest/doc/organization.md

Co-authored-by: Jiuyang Liu <[email protected]>

difftest/doc/organization.md

@@ -1,6 +1,6 @@
 ## Organizational Summary
 
-`difftest` is a verification framework designed to separate the driver and diff test phases. The framework supports testing for two verification objects: `t1` and `t1rocket`. The basic structure and functionality are as follows:
+`difftest` is a verification framework designed to separate the driver and difftest phases. The framework supports testing for two verification objects: `t1` and `t1rocket`. The basic structure and functionality are as follows:
 
 ### Directory Structure