docs/manual: fix typo in migrating-golang-packages

Commit 00230e7 "package/pkg-golang: catch use of legacy FOO_INSTALL_BINS"
introduced a small typo, fixing that.

Signed-off-by: Thomas Devoogdt <thomas@devoogdt.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/manual/migrating.adoc

@@ -227,4 +227,4 @@ your kernel or use an alternative network manager.
 === Migrating to 2025.11
 In 2025.11, the +FOO_INSTALL_BINS+ variable for golang packages is no longer
 supported; the list of binaries to install is automatically derived from
-the +FOO_BULD_TARGETS+ variable.
+the +FOO_BUILD_TARGETS+ variable.