Add a CI check for REMOVE BEFORE FLIGHT

[eggrobin]

We just merged this:

unicodetools/unicodetools/src/main/java/org/unicode/text/UCD/UCD.java

Lines 1312 to 1316 in e9cb075

	// REMOVE BEFORE FLIGHT: The actual version will be greater than 0x100000.
	if (ch <= 0x187FF && rCompositeVersion >= 0x100000) {
	// Unicode [..] added TANGUT IDEOGRAPH-187F8..TANGUT IDEOGRAPH-187FF.
	return TANGUT_BASE;
	}

Might also do DO NOT SUBMIT which is standard Google practice.

(I wrote such a check a in another place year and a half ago, so this is easy.)