Remove deleted pass from rustdoc test suite

`src/test/rustdoc-ui/deprecated-attrs.rs`
tells rustdoc to run the `collapse-docs` pass, which no longer exists
(it was removed in #80261).
Rustdoc doesn't actually give a proper diagnostic here; instead it
prints an `error!` log. Now that tracing is compiled unconditionally,
the log is now being emitted by default, because it's at the error
level.

rustdoc shouldn't be using `error!` logging for diagnostics in the first
place, but in the meantime this change gets the testsuite to pass.

src/test/rustdoc-ui/deprecated-attrs.rs

@@ -1,6 +1,6 @@
 // check-pass
 
-#![doc(no_default_passes, passes = "collapse-docs unindent-comments")]
+#![doc(no_default_passes, passes = "unindent-comments")]
 
 struct SomeStruct;