Remove now outdated comment since we bumped stage0

Author: Urgau

alloc/Cargo.toml

@@ -45,7 +45,6 @@ optimize_for_size = ["core/optimize_for_size"]
 level = "warn"
 # x.py uses beta cargo, so `check-cfg` entries do not yet take effect
 # for rust-lang/rust. But for users of `-Zbuild-std` it does.
-# The unused warning is waiting for rust-lang/cargo#13925 to reach beta.
 check-cfg = [
     'cfg(bootstrap)',
     'cfg(no_global_oom_handling)',

core/Cargo.toml

@@ -41,7 +41,6 @@ debug_refcell = []
 level = "warn"
 # x.py uses beta cargo, so `check-cfg` entries do not yet take effect
 # for rust-lang/rust. But for users of `-Zbuild-std` it does.
-# The unused warning is waiting for rust-lang/cargo#13925 to reach beta.
 check-cfg = [
     'cfg(bootstrap)',
     'cfg(no_fp_fmt_parse)',

std/Cargo.toml

@@ -102,7 +102,6 @@ test = true
 level = "warn"
 # x.py uses beta cargo, so `check-cfg` entries do not yet take effect
 # for rust-lang/rust. But for users of `-Zbuild-std` it does.
-# The unused warning is waiting for rust-lang/cargo#13925 to reach beta.
 check-cfg = [
     'cfg(bootstrap)',
     'cfg(target_arch, values("xtensa"))',