[heap] Remove max executable size configuration.

src/arm64/assembler-arm64.h

Index: src/arm64/assembler-arm64.h
diff --git a/src/arm64/assembler-arm64.h b/src/arm64/assembler-arm64.h
index ea1d94f62817f9db2d2d2aa15ad83430cb2188fa..e4ca410abd3eabb47e4ca366e131b1f578e6977b 100644
--- a/src/arm64/assembler-arm64.h
+++ b/src/arm64/assembler-arm64.h
@@ -2134,6 +2134,9 @@ class Assembler : public AssemblerBase {
   int next_veneer_pool_check_;
 
  private:
+  // Avoid overflows for displacements etc.
+  static const int kMaximalBufferSize = 512 * MB;
+
   // If a veneer is emitted for a branch instruction, that instruction must be
   // removed from the associated label's link chain so that the assembler does
   // not later attempt (likely unsuccessfully) to patch it to branch directly to