.github/workflows: update and fix CI

cmd/age/testdata/encrypted_keys.txt

@@ -2,6 +2,7 @@
 # age file password prompt during encryption
 
 [windows] skip # no pty support
+[go1.20] skip # https://go.dev/issue/61779
 
 # use an encrypted OpenSSH private key without .pub file
 age -R key_ed25519.pub -o ed25519.age input

cmd/age/testdata/scrypt.txt

@@ -1,4 +1,5 @@
 [windows] skip # no pty support
+[go1.20] skip # https://go.dev/issue/61779
 
 # encrypt with a provided passphrase
 stdin input

cmd/age/testdata/terminal.txt

@@ -1,4 +1,5 @@
 [windows] skip # no pty support
+[go1.20] skip # https://go.dev/issue/61779
 
 # controlling terminal is used instead of stdin/stderr
 pty terminal