pam/integration-tests/cli: Increase the wait times on MFA test (#422)

The test is quite unreliable [1] when running in CI or under pressure,
so let's see if we can make it more stable by increasing the wait times,
until vhs will support officially the wait feature.

[1]
https://github.com/ubuntu/authd/actions/runs/9765222175/job/26955414933

UDENG-3549

pam/integration-tests/testdata/tapes/cli/mfa_auth.tape

@@ -54,12 +54,12 @@ Show
 
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-Sleep 300ms
+Sleep 500ms
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-Sleep 300ms
+Sleep 500ms
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@@ -68,12 +68,12 @@ Show
 
 Hide
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-Sleep 300ms
+Sleep 500ms
 Show
 
 Hide
 Enter
-Sleep 300ms
+Sleep 1s
 Show
 
 Hide