Remove old bug files for fixed issues

* 0-atomic-ops-mac-os-x (now using C standard library atomics)
* 0-bugs/ggsmith.m2 (there's now a LocalRings package)
* 0-completion-for-packages (this has been the case for some time)
* 0-delete-error-message ("delete" is now a method)
* 0-doc (fixed at some point -- bug no longer present)
* 0-export-strings ("export" has been accepting only string since 2014)
* 0-factory ("libcfmem" is old -- we can link against factory w/o problems)
* 0-factory-depends (refers to nonexistent file)
* 0-merge-1.5 (merged in 2013! see 5088768)
* 0-ubuntu-dpkg-triggers (distributions/deb package is deprecated)
* 0-update-gpl-license-version (mentioned in LICENSING-NOTES)
* 0-Verbosity (duplicate of #273)
* 0.1-error-message (now get a "no method found" error)
* 0.1-xemacs (xemacs is essentially dead)
* 0.5-debian-script (distributions/deb package is deprecated)
* 0.5-fix-M2-exec-location (fixed by #2163)
* 0.5-package-finding-programs (fixed when "findProgram" was added)
* 0.5-ubuntu-repository (M2 has been in Debian/Ubuntu since 2020)
* 0.7-selectPairs (selectPairs implemented in #3305)
* 1-apropos (can use regex, e.g., apropos "(?i)sort")
* 1-code-and-hooks (implemented in #3118)
* 1-constant-to-RR (promote works since #3457, toRR is compiled so wontfix)
* 1-debian-changelog-file (distributions/deb package is deprecated)
* 1-deb-signatures (distributions/deb package is deprecated)
* 1-factory-bug (bug not present using factory from singular 4.3.2)
* 1-fflas (FFLAS-FFPACK added in 2011 -- see e50558b)
* 1-fpLLL (fpLLL added in 2013 -- see 2447204)
* 1-GPL (we added GPL 3 some time ago)
* 1-include-applications (this has been the behavior for some time)
* 1-Kronecker (added in 2010 -- see d1cb81c)
* 1-nextPrime (added in 2016 -- see 992b43f)
* 1-recursion-in-printing (no more recursion error -- now "no method found")

[ci skip]

Author: d-torrance