[trie.h] pattern definition: fix documentation

[jannick0]

The fix makes the definition of \n consistent with the examples given below the definition. Please note that I did not check this against how it is implemented in the code.

[amitdo]

tesseract/src/dict/trie.cpp

Lines 380 to 381 in 912c997

	} else if (ch == 'n') {
	return alphanum_pattern_;