ci: Fix release-plz configuration

Author: tgross35

.release-plz.toml

@@ -1,10 +1,12 @@
-[[package]]
-name = "compiler_builtins"
-semver_check = false
+[workspace]
 # As part of the release process, we delete `libm/Cargo.toml`. Since
 # this is only run in CI, we shouldn't need to worry about it.
 allow_dirty = true
 publish_allow_dirty = true
 
+[[package]]
+name = "compiler_builtins"
+semver_check = false
+
 [[package]]
 name = "libm"