Revert "[wasm] Increase code space limit to 1024 MB"

This reverts commit 15d6d7b4.

Reason for revert: speculative revert for this failure: https://logs.chromium.org/logs/v8/buildbucket/cr-buildbucket.appspot.com/8934981003100286416/+/steps/Check/0/logs/Fixed/0

Original change's description:
> [wasm] Increase code space limit to 1024 MB
> 
> Liftoff increases code size, and people start deploying bigger modules.
> Increase the wasm code space limit from 512 MB to 1024 MB to account
> for this.
> 
> R=​titzer@chromium.org
> 
> Bug: chromium:883639, chromium:872684
> Change-Id: I3a2ca29d456635f7f3aa1daef5fa2b0249dc1645
> Reviewed-on: https://chromium-review.googlesource.com/1226971
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Reviewed-by: Ben Titzer <titzer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#56003}

TBR=titzer@chromium.org,clemensh@chromium.org

Change-Id: I77b3eb694edef122fb3467ca1938c5aff833911d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:883639, chromium:872684
Reviewed-on: https://chromium-review.googlesource.com/1232958Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56014}

src/globals.h

@@ -153,7 +153,7 @@ constexpr int kDoubleSizeLog2 = 3;
 // ARM64 only supports direct calls within a 128 MB range.
 constexpr size_t kMaxWasmCodeMemory = 128 * MB;
 #else
-constexpr size_t kMaxWasmCodeMemory = 1024 * MB;
+constexpr size_t kMaxWasmCodeMemory = 512 * MB;
 #endif
 
 #if V8_HOST_ARCH_64_BIT