Revert accidental change of go version in go.mod (wasn't supposed to commit).

Version set properly to 1.18, which is the new minimum needed for changes in this branch.
Run go mod tidy again with version set back to 1.18.

go.mod

@@ -1,8 +1,6 @@
 module github.com/shirou/gopsutil/v3
 
-go 1.21.0
-
-toolchain go1.22.3
+go 1.18
 
 require (
 	github.com/google/go-cmp v0.6.0

go.sum

@@ -14,7 +14,6 @@ github.com/power-devops/perfstat v0.0.0-20210106213030-5aafc221ea8c/go.mod h1:Om
 github.com/shoenig/go-m1cpu v0.1.6 h1:nxdKQNcEB6vzgA2E2bvzKIYRuNj7XNJ4S/aRSwKzFtM=
 github.com/shoenig/go-m1cpu v0.1.6/go.mod h1:1JJMcUBvfNwpq05QDQVAnx3gUHr9IYF7GNg9SUEw2VQ=
 github.com/shoenig/test v0.6.4 h1:kVTaSd7WLz5WZ2IaoM0RSzRsUD+m8wRR+5qvntpn4LU=
-github.com/shoenig/test v0.6.4/go.mod h1:byHiCGXqrVaflBLAMq/srcZIHynQPQgeyvkvXnjqq0k=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/tklauser/go-sysconf v0.3.12 h1:0QaGUFOdQaIVdPgfITYzaTegZvdCjmYO52cSFAEVmqU=