Update source/overview.txt

Co-authored-by: Evelyn Rabil <[email protected]>

Author: jvincent-mongodb

source/overview.txt

@@ -6,7 +6,7 @@
 
 .. default-domain:: mongodb
 
-|cloudgov| is a a fully-managed cloud database for the U.S. 
+|cloudgov| is a fully-managed cloud database for the U.S. 
 government (federal agencies and state, local, and education (SLED)
 entities).