[NO UPSTREAM] buck2: drop elf_sections from the OSS build

Upstream embeds `buck2_miniperf` into `buck2-bin` as a compressed ELF
section. The bootstrap build cannot do this: `[external_cells] prelude =
bundled` takes the prelude from the pinned `bootstrap/buck2` snapshot,
which predates the `elf_sections` attr, and there is no newer release to
bump to.

Nothing is lost: `MiniperfContainer::new` is `#[cfg(all(fbcode_build,
target_os = "linux"))]` and returns `Ok(None)` otherwise, so an OSS
buck2 never reads the section.

Signed-off-by: Austin Seipp <aseipp@pobox.com>

Author: thoughtpolice

app/buck2/BUCK

@@ -101,12 +101,6 @@ buck_rust_binary(
     allow_cache_upload = True,
     crate = "buck2",
     crate_root = "bin/buck2.rs",
-    elf_sections = select({
-        "DEFAULT": {},
-        "ovr_config//os:linux": {
-            "buck2_miniperf": "//buck2/app/buck2_miniperf:embedded_section",
-        },
-    }),
     env = {
         # This is only set for release builds.
         "BUCK2_RELEASE_TIMESTAMP": read_config("buck", "release_timestamp", ""),