chore: upgrade to go1.18.2 (#750)

I have not upgraded ooni/go yet because I am also checking whether it
would be possible instead to use ooni/oocrypto as documented in the
https://github.com/ooni/probe/issues/2106 issue.

Closes https://github.com/ooni/probe/issues/2070

Closes https://github.com/ooni/probe/issues/2077

.github/workflows/netxlite.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: "${{ matrix.os }}"
     strategy:
       matrix:
-        go: [ "1.17.10" ]
+        go: [ "1.18.2" ]
         os: [ "ubuntu-20.04", "windows-2019", "macos-10.15" ]
     steps:
       - uses: magnetikonline/action-golang-cache@v2