gregorio: unbundle from texlive_core

Putting the new recipe in `dev-tex` is an estimation, there is no separate package in Gentoo.

app-text/texlive_core/texlive_core-2024.2.recipe

@@ -158,7 +158,6 @@ PROVIDES="
 	cmd:gftopk
 	cmd:gftype
 	cmd:git_latexdiff
-	cmd:gregorio
 	cmd:gsftopk
 	cmd:hilatex
 	cmd:hishrink
@@ -590,7 +589,6 @@ defineDebugInfoPackage texlive_core$secondaryArchSuffix \
 	$prefix/bin/gftodvi \
 	$prefix/bin/gftopk \
 	$prefix/bin/gftype \
-	$prefix/bin/gregorio \
 	$prefix/bin/gsftopk \
 	$prefix/bin/hishrink \
 	$prefix/bin/histretch \
@@ -861,6 +859,7 @@ BUILD()
 		--disable-dvi2tty \
 		--disable-dvipng \
 		--disable-dvisvgm \
+		--disable-gregorio \
 		--disable-t1utils \
 		--build=$HOST --host=$HOST