update comment

ch10_rnn/embedding_example.ipynb

@@ -151,7 +151,7 @@
     }
    ],
    "source": [
-    "# 文字嵌入其实就是张量乘法\n",
+    "# 文本嵌入其实就是张量乘法\n",
     "x                                 # ( 4, 26)\n",
     "W = torch.randn((num_claz, dims)) # (26,  5)\n",
     "x @ W                             # ( 4,  5)"