build: Unbreak 'go build' by using micro version in go.mod's go line

Currently, 'go build' is failing on Fedora 42 Workstation:
  $ meson compile -C builddir --verbose
  ...
  /path/src/go-build-wrapper /path/src /path/builddir src/toolbox 0.1.1
      cc /lib64/ld-linux-x86-64.so.2 false
  go: updates to go.mod needed; to update it:
          go mod tidy
  ninja: build stopped: subcommand failed.

... with Go version:
  $ go version
  go version go1.24.3 linux/amd64
  $ rpm -q golang
  golang-1.24.3-2.fc42.x86_64

Strangely, the CI hasn't been failing on Fedora 42 with the same Go
version [1].

Starting from Go version 1.21.0, Go started using an explicit 0 micro
version instead of skipping it - compare Go 1.20 and 1.21.0 [2].  It
looks like recent versions of Go are pedantic about using the exact
version number.

[1] #1657

[2] https://github.com/golang/go/releases/tag/go1.20
    https://github.com/golang/go/releases/tag/go1.21.0

#1659

Author: debarshiray

src/go.mod

@@ -1,6 +1,6 @@
 module github.com/containers/toolbox
 
-go 1.21
+go 1.21.0
 
 require (
 	github.com/HarryMichal/go-version v1.0.1