test: lua: (trivial) fix indentation

Replace a TAB with spaces.

Change-Id: I3d5c79af4116614ef78dd8a71eb42e93875c0637
Reviewed-on: https://code.wireshark.org/review/30790
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>

test/lua/tvb.lua

@@ -206,7 +206,7 @@ local getfield =
     {
         STRING         = Field.new ("test.basic.string"),
         BOOLEAN        = Field.new ("test.basic.boolean"),
-	UINT8          = Field.new ("test.basic.uint8"),
+        UINT8          = Field.new ("test.basic.uint8"),
         UINT16         = Field.new ("test.basic.uint16"),
         INT24          = Field.new ("test.basic.uint24"),
         BYTES          = Field.new ("test.basic.bytes"),