tjbench.c: Remove vestigial int overflow checks

Since tj3Alloc() now accepts a size_t argument rather than an int
argument, it is no longer necessary to check for signed integer overflow
in the C version of TJBench.
diff --git a/tjbench.c b/tjbench.c
index f12f5c2..e0573b4 100644
--- a/tjbench.c
+++ b/tjbench.c
@@ -410,8 +410,6 @@
 
         if (jpegBufSize == 0)
           THROW_TJG();
-        if (jpegBufSize > (size_t)INT_MAX)
-          THROW("getting buffer size", "Image is too large");
         if ((jpegBufs[i] = tj3Alloc(jpegBufSize)) == NULL)
           THROW_UNIX("allocating JPEG tiles");
       }
@@ -722,8 +720,6 @@
 
         if (jpegBufSize == 0)
           THROW_TJG();
-        if (jpegBufSize > (size_t)INT_MAX)
-          THROW("getting buffer size", "Image is too large");
         if ((jpegBufs[i] = tj3Alloc(jpegBufSize)) == NULL)
           THROW_UNIX("allocating JPEG tiles");
       }