upgrading Go to 1.19

We switched to GO 1.18 in August, 2022 which is now EOL.

Our CI has switched to start running with Go 1.19.

Given these two motivations, upgrading pipelines to use 1.19

Signed-off-by: pritidesai <pdesai@us.ibm.com>

go.mod

@@ -1,6 +1,6 @@
 module github.com/tektoncd/pipeline
 
-go 1.18
+go 1.19
 
 require (
 	github.com/Microsoft/go-winio v0.6.0 // indirect