fix https://github.com/timotheecour/Nim/issues/152: avoid writing spurious ^[[0m to stderr when callStyledWriteLineStderr not called (#14214)

* fix https://github.com/timotheecour/Nim/issues/152 `^[[0m` is inserted in stderr for `echo code | nim c -`

* resetAttributes not even needed, already handled in styledWriteLine

* simplify tests in tests/trunner.nim thanks to this fix

compiler/main.nim

@@ -405,5 +405,3 @@ proc mainCommand*(graph: ModuleGraph) =
     echo "  int tries: ", gCacheIntTries
     echo "  efficiency: ", formatFloat(1-(gCacheMisses.float/gCacheTries.float),
                                        ffDecimal, 3)
-
-  resetAttributes(conf)