Remove too generic hyphenation rule for Russian "э" vowel

[dmalinovsky]

With this rule the engine makes hyphenations in unexpected places:

With the rule	Without it

It also makes hyphens in the words like this: "фл-эшка" ("fl-ash drive"), "Бл-эк" ("Bl-ack"), "Гр-эй" ("Gr-ay").

@hius07, can you please take a look or recommend another reviewer?

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This change is 

[hius07]

Are there examples of usual words affected by the 1э pattern?

[dmalinovsky]

I didn’t find a way to run the hyphenation engine manually, but I imagine it may affect the words like “поэзия” or “маэстро”: https://gramota.ru/biblioteka/spravochniki/pravila-russkoj-orfografii-i-punktuacii/bukva-e

[poire-z]

Feels odd you need to update such a generic pattern - and that Russian readers/writters (using KOReader or Libreoffice or other softwares) didn't feel the need to change that for 20 years :)
Would be goot to check how it is in the current free hyph dicts used by such projects. Some links in #373.
And for other russian readers to use these modified .pattern files on their current reading for some time.

(Usually, at least for French, we have just added "longer" patterns for "strange" words these last years.)
Also, for quick checking individual words: https://www.ushuaia.pl/hyphen/

[dmalinovsky]

This pattern negatively affects mostly foreign names, which are not in the dictionaries.

Thanks for the suggestion, @poire-z, I’ll work on adding longer patterns instead of this PR.