Bump version of Golang container to match module version

The Go module for v2 is 1.19, bumping the base docker image to match the
minimum version ensures go-getter can be compiled and executed on the
container. This change resolves the failing acceptance test for Samba.

```
Run docker exec -i gogetter bash -c "env ACC_SMB_TEST=1 go test -v ./... -run=TestSmb_"
  docker exec -i gogetter bash -c "env ACC_SMB_TEST=1 go test -v ./... -run=TestSmb_"
  shell: /usr/bin/bash -e {0}
  env:
    TEST_RESULTS_PATH: /tmp/test-results
Error: ./get_git.go:366:16: undefined: os.ReadDir
Error: ./get_git_test.go:886:9: undefined: os.WriteFile
Error: ./get_git_test.go:904:22: undefined: os.ReadFile
note: module requires Go 1.19
FAIL	github.com/hashicorp/go-getter/v2 [build failed]
?   	github.com/hashicorp/go-getter/v2/helper/testing	[no test files]
testing: warning: no tests to run
PASS
ok  	github.com/hashicorp/go-getter/v2/helper/url	0.006s [no tests to run]
FAIL
Error: Process completed with exit code 2.

```

Dockerfile

@@ -1,5 +1,5 @@
 # Dockerfile to create a go-getter container with smbclient dependency that is used by the get_smb.go tests
-FROM golang:1.15
+FROM golang:1.19.13
 
 COPY . /go-getter
 WORKDIR /go-getter