Filter out postin-without-install-info

Fedora no longer requires install-info scriptlets, and we already filter out some rpmlint rules (`info-files-without-install-info-postin` and `info-files-without-install-info-postun`).

Some packages (like `emacs-slime`) still has `%post` for other reasons, though, and if they also ship info files this triggers an extraneous rpmlint error.

Filter out `postin-without-install-info` in addition to the existing two rules.

Test case:
```
~/src/fedora/pkgs-others/rpmlint master*
❯ diff -u <(rpmlint /var/lib/mock/fedora-32-x86_64/result/emacs-slime-2.24-1.fc32.noarch.rpm) <(rpmlint -f ./rpmlint.config /var/lib/mock/fedora-32-x86_64/result/emacs-slime-2.24-1.fc32.noarch.rpm)
--- /proc/self/fd/12    2020-04-28 18:24:01.774132790 -0700
+++ /proc/self/fd/13    2020-04-28 18:24:01.775132781 -0700
@@ -1,6 +1,4 @@
 emacs-slime.noarch: E: incorrect-fsf-address /usr/share/common-lisp/source/slime/lib/hyperspec.el
 emacs-slime.noarch: E: incorrect-fsf-address /usr/share/common-lisp/source/slime/swank/clisp.lisp
 emacs-slime.noarch: E: incorrect-fsf-address /usr/share/emacs/site-lisp/slime/lib/hyperspec.el
-emacs-slime.noarch: E: postin-without-install-info /usr/share/info/slime.info.gz
-emacs-slime.noarch: E: postin-without-install-info /usr/share/info/slime.info.gz
-1 packages and 0 specfiles checked; 5 errors, 0 warnings.
+1 packages and 0 specfiles checked; 3 errors, 0 warnings.
```

rpmlint.config

@@ -456,6 +456,7 @@ addFilter("non-standard-dir-perm /var/lib/.* 700")
 # Fedora no longer requires install-info scriptlets
 addFilter("info-files-without-install-info-postin")
 addFilter("info-files-without-install-info-postun")
+addFilter("postin-without-install-info")
 
 bad_crypto_warning = \
 '''This application package calls a function to explicitly set crypto ciphers