[CALCITE-6565] Invalid unparse for CHAR without precision in MssqlSqlDialect #13461

Job	Run time
CheckerFramework (JDK 11)	12m 49s
Error Prone (JDK 11), latest Guava	6m 21s
Linux (JDK 11), Avatica main	14m 16s
CheckerFramework (JDK 11), oldest Guava	12m 47s
Druid Tests	9m 10s
Linux (JDK 11), Pacific/Chatham Timezone	12m 49s
Linux (JDK 21)	12m 11s
Linux (JDK 17)	10m 25s
Linux (JDK 22)	10m 15s
Linux (JDK 8), latest Guava, America/New_York Timezone	11m 49s
Linux (JDK 8), oldest Guava, America/New_York Timezone	10m 41s
Linux (JDK 8) Slow Tests	0s
macOS (JDK 21)	44m 42s
Windows (JDK 17)	15m 5s
Windows (JDK 21)	16m 29s
Windows (JDK 8)	15m 23s
	3h 35m 12s

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