Fix download URLs.

The zlib URL changed because the version being downloaded is outdated and old
versions are moved into the "fossils" directory.

The pffft URL changed because it was downloading from a Mercurial repository and
Bitbucket deleted all Mercurial repositories. The developer recreated it as a
git repository which changed the commit hashes. The 29e4f76ac53b commit of the
pffft hg repository was added to Rack in 2018. In the pffft git repository,
74d7261be17c is the most recent commit that would have been available as of
2018. For confirmation that this is the correct git commit to correspond to the
old hg commit:

https://github.com/google/visqol/pull/19#issuecomment-680207988

--- dep/Makefile.orig	2023-08-01 15:54:53.000000000 -0500
+++ dep/Makefile	2023-08-01 15:57:11.000000000 -0500
@@ -146,7 +146,7 @@
 	$(MAKE) -C libzip-1.5.2/build install
 
 zlib-1.2.11:
-	$(WGET) "https://www.zlib.net/zlib-1.2.11.tar.gz"
+	$(WGET) "https://www.zlib.net/fossils/zlib-1.2.11.tar.gz"
 	$(SHA256) zlib-1.2.11.tar.gz c3e5e9fdd5004dcb542feda5ee4f0ff0744628baf8ed2dd5d66f8ca1197cb1a1
 	$(UNTAR) zlib-1.2.11.tar.gz
 	rm zlib-1.2.11.tar.gz
@@ -235,18 +235,18 @@
 $(osdialog): $(wildcard osdialog/*.h)
 	cp $^ include/
 
-jpommier-pffft-29e4f76ac53b:
-	$(WGET) "https://bitbucket.org/jpommier/pffft/get/29e4f76ac53b.zip"
-	$(SHA256) 29e4f76ac53b.zip bb10afba127904a0c6c553fa445082729b7d72373511bda1b12a5be0e03f318a
-	$(UNZIP) 29e4f76ac53b.zip
-	rm 29e4f76ac53b.zip
+jpommier-pffft-74d7261be17c:
+	$(WGET) "https://bitbucket.org/jpommier/pffft/get/74d7261be17c.zip"
+	$(SHA256) 74d7261be17c.zip 0521a0ae522c74ed2a26130109b6366110ba43445826d98144ad65ef53186136
+	$(UNZIP) 74d7261be17c.zip
+	rm 74d7261be17c.zip
 
-$(pffft): jpommier-pffft-29e4f76ac53b
-	cp jpommier-pffft-29e4f76ac53b/*.h include/
+$(pffft): jpommier-pffft-74d7261be17c
+	cp jpommier-pffft-74d7261be17c/*.h include/
 
 # Helpers
 
-src: glew-2.1.0 glfw jansson-2.12 speexdsp-SpeexDSP-1.2rc3 openssl-1.1.1d curl-7.66.0 libzip-1.5.2 zlib-1.2.11 rtmidi-4.0.0 rtaudio nanovg nanosvg oui-blendish osdialog jpommier-pffft-29e4f76ac53b
+src: glew-2.1.0 glfw jansson-2.12 speexdsp-SpeexDSP-1.2rc3 openssl-1.1.1d curl-7.66.0 libzip-1.5.2 zlib-1.2.11 rtmidi-4.0.0 rtaudio nanovg nanosvg oui-blendish osdialog jpommier-pffft-74d7261be17c
 
 clean:
 	git clean -fdx