Correct go install instructions (#3309)

Go 1.21+ is required for recent versions of sqlc. This is because it uses components that require the 1.21 toolchain. Coincidentally 1.21 is also when forward compatibility was introduced.

Author: jdahm

docs/overview/install.md

@@ -14,20 +14,14 @@ brew install sqlc
 sudo snap install sqlc
 ```
 
-## go install 
+## go install
 
-### Go >= 1.17:
+Installing recent versions of sqlc requires Go 1.21+.
 
 ```
 go install github.com/sqlc-dev/sqlc/cmd/sqlc@latest
 ```
 
-### Go < 1.17:
-
-```
-go get github.com/sqlc-dev/sqlc/cmd/sqlc
-```
-
 ## Docker
 
 ```