Revert "[runtime] Do some more StringTable shrinking"

This reverts commit 6823c0a4.

Reason for revert: https://crbug.com/830499

Original change's description:
> [runtime] Do some more StringTable shrinking
> 
> This CL further lowers the kMaxEmptyFactor constant to more aggressively shrink
> the StringTable when it's empty.
> 
> Bug: v8:5443, chromium:818642
> Change-Id: I1c263a0afd7e6bed8a8bb857db032bf126c3ef4b
> Reviewed-on: https://chromium-review.googlesource.com/995473
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Camillo Bruni <cbruni@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#52401}

TBR=mlippautz@chromium.org,cbruni@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: v8:5443, chromium:818642
Change-Id: Ibd009fe1e9fcd0b36f168ad425e1eb5e663a1ca8
Reviewed-on: https://chromium-review.googlesource.com/1004456Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52515}

src/objects/string-table.h

@@ -79,7 +79,7 @@ class StringTable : public HashTable<StringTable, StringTableShape> {
 
   DECL_CAST(StringTable)
 
-  static const int kMaxEmptyFactor = 4;
+  static const int kMaxEmptyFactor = 8;
   static const int kMinCapacity = 2048;
   static const int kMinShrinkCapacity = kMinCapacity;