Add missing newline in code example in string module documentation

PiperOrigin-RevId: 685784112
Change-Id: I7472b8789b5d14e8f0b898ab716eb4a22103d15f

src/main/java/net/starlark/java/eval/StringModule.java

@@ -48,7 +48,7 @@
             + "# Strings support slicing (negative index starts from the end):\n"
             + "x = \"hello\"[2:4]  # \"ll\"\n"
             + "y = \"hello\"[1:-1]  # \"ell\"\n"
-            + "z = \"hello\"[:4]  # \"hell\""
+            + "z = \"hello\"[:4]  # \"hell\"\n"
             + "# Slice steps can be used, too:\n"
             + "s = \"hello\"[::2] # \"hlo\"\n"
             + "t = \"hello\"[3:0:-1] # \"lle\"\n</pre>"