Update the default branch to 1.x

[seth-shaw-unlv]

GitHub Issue: Islandora/documentation#1907

What does this Pull Request do?

Updates the GitHub actions and other bits to use the new 1.x branch. Also changes some references from "Islandora 8" to "Islandora"

How should this be tested?

GitHub Actions green means go.

Interested parties

@rosiel @bseeger but perhaps also @dannylamb or @DonRichards

[codecov]

Codecov Report

Merging #81 (dffa109) into 1.x (c4b16ea) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                1.x      #81   +/-   ##
=========================================
  Coverage     89.80%   89.80%           
  Complexity       79       79           
=========================================
  Files            11       11           
  Lines           304      304           
  Branches          1        1           
=========================================
  Hits            273      273           
  Misses           30       30           
  Partials          1        1           

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