Use only minor version in go module

This change removes the patch version specifier from the go version in the go.mod file.

See https://go.dev/ref/mod#go-mod-file-go

Signed-off-by: Evan Lezar <elezar@nvidia.com>

go.mod

@@ -1,3 +1,3 @@
 module github.com/xrash/smetrics
 
-go 1.15.0
+go 1.15