diag.t: Remove more nonexistent exceptions
perlfunc: Document fallback to "top" format

perl 4’s perl.man says this:

By default the top‐of‐page format is "top", but it may be set to the
format of your choice by assigning the name to the $^ variable.

This is still the case, but is completely undocumented in perl 5.

In perl 5 the presence of a <FILEHANDLE_NAME>_TOP format will over-
ride "top", as will $^, but "top" is still checked for in the
absence of those.

This should be documented.  One thing I do mention here that perl 4
omits is that it is "top" in the current package.

I also tweaked the wording of the preceding sentence.
perldiag: Document ‘Can't call mro_isa_changed_in’
perldelta for #118159 (SvTRUE on ""/1 dualvar)
perldelta for 3036c853/\N{} deprecations
perldelta for deparsing for my $x (#117081)
perldelta for constant inlining (70e5f2b5)
perldelta for two lexsub fixes
perldelta for lexsub syntax errors (3a74e0e282c)
perldelta: typo
perldelta for #117311/B::Deparse -l and FF
perldelta for JS in perltrap
perldelta for deparsing ${#}{foo} (#117531)
perldelta for #117595 (-l warning)
perldelta for (?[]) fixes
perldealt for delete local $ENV{x} leaking (9332b95f7)
perldelta for sort/require CORE:: (#24482)
perldelta for freed stashes (#117941)
perldelta for PL_stashcacheh and glob-to-glob assignment (210fdecd4)
Increase $File::Spec::VERSION to 3.41

to match the version number increases in some of the submodules and
to make the perldelta entry easier to describe.