Update vignette advice for migrating to {testthat} 3e

[jdblischak]

I have recently been working on migrating some packages from {testthat} 2e to 3e. This PR updates a few places in the vignettes where I got confused.

First is the behavior of expect_equal(ignore_attr = TRUE). From what I can decipher from the history, this initially ignored the attribute names. However, now it appears to ignore all attributes just like expect_equivalent(). I'm not sure exactly when this change occurred since this functionality was migrated to {waldo}.

library("testthat")
packageVersion("testthat")
## [1] ‘3.2.3.9000’
edition_get()
## [1] 3

x1 <- x2 <- mtcars
colnames(x2) <- NULL
expect_equivalent(x1, x2)
## Warning message:
##   `expect_equivalent()` was deprecated in the 3rd edition.
## ℹ Use expect_equal(ignore_attr = TRUE)
expect_equal(x1, x2)
## Error: `x1` (`actual`) not equal to `x2` (`expected`).
##
## `names(actual)` is a character vector ('mpg', 'cyl', 'disp', 'hp', 'drat', ...)
## `names(expected)` is absent
expect_equal(x1, x2, ignore_attr = TRUE)

xref: #1241, #1422, r-lib/waldo#97

Second is the advice for interactive debugging when the tests are configured to run in parallel. I wasn't able to use browser() with CheckReporter because it still ran the tests in parallel. I was able to use browser() with the DebugReporter.

# Added browser() to first test in test-expect-condition.R

# CheckReporter
devtools::test(filter = "expect", reporter = "check")
## ℹ Testing testthat
## Starting 8 test processes
## [ FAIL 1 | WARN 0 | SKIP 1 | PASS 519 ]
## 
## ══ Skipped tests (1) ══════════════════════════════════════════════════════════════════════════════
## • On Windows (1): test-expect-known.R:46:3
## 
## ══ Failed tests ═══════════════════════════════════════════════════════════════════════════════════
## ── Error (test-expect-condition.R:2:3): returns condition or value ────────────────────────────────
## Error in `eval(code, test_env)`: non-interactive browser() -- left over from debugging?
## 
## [ FAIL 1 | WARN 0 | SKIP 1 | PASS 519 ]

# DebugReporter
devtools::test(filter = "expect", reporter = "debug")
## ℹ Testing testthat
## Called from: eval(code, test_env)
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