docs: fixed typos in core-principles.md (#316) #1059

Job	Run time
check	4m 16s
cli-test	15m 15s
test	10m 4s
e2e-example-test (basic, core)	7m 59s
e2e-example-test (capsules, core)	9m 48s
e2e-example-test (custom_server, core)	5m 56s
e2e-example-test (error_views, core)	8m 0s
e2e-example-test (freezing_and_thawing, core)	7m 42s
e2e-example-test (global_state, core)	8m 27s
e2e-example-test (helper_build_state, core)	8m 30s
e2e-example-test (i18n, core)	8m 51s
e2e-example-test (idb_freezing, core)	7m 58s
e2e-example-test (index_view, core)	7m 33s
e2e-example-test (js_interop, core)	7m 39s
e2e-example-test (plugins, core)	7m 30s
e2e-example-test (preload, core)	6m 43s
e2e-example-test (router_state, core)	4m 40s
e2e-example-test (rx_state, core)	6m 38s
e2e-example-test (set_headers, core)	6m 35s
e2e-example-test (state_generation, core)	9m 15s
e2e-example-test (static_content, core)	6m 25s
e2e-example-test (suspense, core)	5m 59s
e2e-example-test (unreactive, core)	6m 26s
	2h 58m 9s

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