* doc/misc/erc.texi: Update ERCVER to 5.5. * lisp/erc/erc.el: Increment main version header to 5.5. Update Compat version in package-requires header to 29.1.3.4. Update `customize-package-emacs-version-alist' entry by mapping ERC 5.5 to Emacs 29.1. (erc-version): Update value to 5.5.