docs/frag...merging.rst - s/contructed/constructed
This PR corrects "contructed" to "constructed".
Fragment Merging
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-Once the matrix of YAML fragments is contructed by teuthology, the fragments
+Once the matrix of YAML fragments is constructed by teuthology, the fragments
must be merged together and processed. Up until 2022, this merging process was
static: all of the YAML fragments were joined together in lexicographical order
with duplicate fragment members *deep merged* together (e.g. the "tasks"
