Remove redundant c_enum_min_bits option from the thumbv4t-none-eabi target.

This option is the same as the `thumb_base` defaults used by this target.

compiler/rustc_target/src/spec/thumbv4t_none_eabi.rs

@@ -45,8 +45,6 @@ pub fn target() -> Target {
             relocation_model: RelocModel::Static,
             // suggested from thumb_base, rust-lang/rust#44993.
             emit_debug_gdb_scripts: false,
-            // suggested from thumb_base, with no-os gcc/clang use 8-bit enums
-            c_enum_min_bits: Some(8),
             frame_pointer: FramePointer::MayOmit,
 
             main_needs_argc_argv: false,