Update zenoh:master references in README to zenoh:main. #366

Job	Run time
Check c99 compilation	12s
Test multicast and unicast fragmentation	35s
Check codebase format with clang-format	7s
Build and test raweth transport on ubuntu-latest (1)	29s
Build and test raweth transport on ubuntu-latest (0)	31s
Modular build on ubuntu-latest (1, 1, 1, 1)	36s
Run unit tests on ubuntu-latest	36s
Modular build on ubuntu-latest (1, 1, 1, 0)	29s
Modular build on ubuntu-latest (1, 1, 0, 1)	1m 1s
Build and test in single thread on ubuntu-latest	25s
Modular build on ubuntu-latest (1, 1, 0, 0)	31s
Modular build on ubuntu-latest (1, 0, 1, 1)	36s
Modular build on ubuntu-latest (1, 0, 1, 0)	28s
Modular build on ubuntu-latest (1, 0, 0, 1)	37s
Modular build on ubuntu-latest (1, 0, 0, 0)	59s
Modular build on ubuntu-latest (0, 1, 1, 1)	22s
Modular build on ubuntu-latest (0, 1, 1, 0)	20s
Modular build on ubuntu-latest (0, 1, 0, 1)	1m 8s
Modular build on ubuntu-latest (0, 1, 0, 0)	42s
Modular build on ubuntu-latest (0, 0, 1, 1)	36s
Modular build on ubuntu-latest (0, 0, 1, 0)	41s
Modular build on ubuntu-latest (0, 0, 0, 1)	26s
Modular build on ubuntu-latest (0, 0, 0, 0)	17s
	12m 44s

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