build, macos: Drop unused `osx_volname` target #29733

The osx_volname makefile target was introduced in #7192 and was used to pass the package name to Gitian scripts as a content of the osx_volname file.

With the current Guix scripts, the osx_volname file is never read. Therefore, its creation might be omitted.

My Guix builds:

x86_64
5e2d254e207d53784621c8df331c9bf4a969da667d185992402f48a5ac49f563  guix-build-eff19fa1c8d7/output/arm64-apple-darwin/SHA256SUMS.part
089dba70685893aca5e7c8ce1d53a07380e87ca50eda8b3a2a75aeaeb1d28e48  guix-build-eff19fa1c8d7/output/arm64-apple-darwin/bitcoin-eff19fa1c8d7-arm64-apple-darwin-unsigned.tar.gz
390c57197c6ab4aefdde1c665d5e4ebdfb4ae5e553f8f93b017f2fad1093d110  guix-build-eff19fa1c8d7/output/arm64-apple-darwin/bitcoin-eff19fa1c8d7-arm64-apple-darwin-unsigned.zip
e1edde7ca28bf26aea8d956b1d3c1725a475f2a9c148f5c36b651db4b814091c  guix-build-eff19fa1c8d7/output/arm64-apple-darwin/bitcoin-eff19fa1c8d7-arm64-apple-darwin.tar.gz
d0096ea73a5f75cc4d3cef4ef1761ae3e48c8a63aff918f07371c5c88896e4e6  guix-build-eff19fa1c8d7/output/dist-archive/bitcoin-eff19fa1c8d7.tar.gz
51b4affb9fd6f8aea05b7d25d29f017d0a0a145395f457caa14b9af9646b035b  guix-build-eff19fa1c8d7/output/x86_64-apple-darwin/SHA256SUMS.part
b1df081ecf636a92754e673e5388d1d988653d4646f0b0446a4c9f14d865a265  guix-build-eff19fa1c8d7/output/x86_64-apple-darwin/bitcoin-eff19fa1c8d7-x86_64-apple-darwin-unsigned.tar.gz
62e09926029d176da950d3e3db7ff8ae6cbe4c0b2ea17b084fc1d28565f91475  guix-build-eff19fa1c8d7/output/x86_64-apple-darwin/bitcoin-eff19fa1c8d7-x86_64-apple-darwin-unsigned.zip
477dcb2382cbd447bd88a3b644b4bd736f5b67d66d42cb73fe31ffc153d3e181  guix-build-eff19fa1c8d7/output/x86_64-apple-darwin/bitcoin-eff19fa1c8d7-x86_64-apple-darwin.tar.gz

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ACK eff19fa1c8d736d30dea937ebce0b372c19b7559

ACK https://github.com/bitcoin/bitcoin/pull/29733/commits/eff19fa1c8d736d30dea937ebce0b372c19b7559

tACK eff19fa1c8d736d30dea937ebce0b372c19b7559

Tested that make deploy still works on (Intel) macOS 14.4.1.

5e2d254e207d53784621c8df331c9bf4a969da667d185992402f48a5ac49f563  guix-build-eff19fa1c8d7/output/arm64-apple-darwin/SHA256SUMS.part
089dba70685893aca5e7c8ce1d53a07380e87ca50eda8b3a2a75aeaeb1d28e48  guix-build-eff19fa1c8d7/output/arm64-apple-darwin/bitcoin-eff19fa1c8d7-arm64-apple-darwin-unsigned.tar.gz
390c57197c6ab4aefdde1c665d5e4ebdfb4ae5e553f8f93b017f2fad1093d110  guix-build-eff19fa1c8d7/output/arm64-apple-darwin/bitcoin-eff19fa1c8d7-arm64-apple-darwin-unsigned.zip
e1edde7ca28bf26aea8d956b1d3c1725a475f2a9c148f5c36b651db4b814091c  guix-build-eff19fa1c8d7/output/arm64-apple-darwin/bitcoin-eff19fa1c8d7-arm64-apple-darwin.tar.gz
d0096ea73a5f75cc4d3cef4ef1761ae3e48c8a63aff918f07371c5c88896e4e6  guix-build-eff19fa1c8d7/output/dist-archive/bitcoin-eff19fa1c8d7.tar.gz
51b4affb9fd6f8aea05b7d25d29f017d0a0a145395f457caa14b9af9646b035b  guix-build-eff19fa1c8d7/output/x86_64-apple-darwin/SHA256SUMS.part
b1df081ecf636a92754e673e5388d1d988653d4646f0b0446a4c9f14d865a265  guix-build-eff19fa1c8d7/output/x86_64-apple-darwin/bitcoin-eff19fa1c8d7-x86_64-apple-darwin-unsigned.tar.gz
62e09926029d176da950d3e3db7ff8ae6cbe4c0b2ea17b084fc1d28565f91475  guix-build-eff19fa1c8d7/output/x86_64-apple-darwin/bitcoin-eff19fa1c8d7-x86_64-apple-darwin-unsigned.zip
477dcb2382cbd447bd88a3b644b4bd736f5b67d66d42cb73fe31ffc153d3e181  guix-build-eff19fa1c8d7/output/x86_64-apple-darwin/bitcoin-eff19fa1c8d7-x86_64-apple-darwin.tar.gz