Fix the soname

Commit 1832e2d3 accidentally bumped rsvg_lt_age without updating
rsvg_lt_current, which led to the soname accidentally changing from
librsvg-2.so.2 to librsvg-2.so.1.

Fixes: #402
7 jobs for <span class="ref-name">wip/kalev/fix-soname</span> in 26 minutes and 48 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #184218
fedora test

00:05:35

 
  Lint
manual #184220
allowed to fail manual
clippy
passed #184219
rustfmt

00:00:50

passed #184221
tarball

00:12:08

 
  Cross Distro
passed #184224
debian_i386:testing

00:09:03

passed #184223
debian:testing

00:05:46

passed #184222
fedora:rawhide

00:05:47