BOSTON — Gyms, movie theaters, museums and other indoor event spaces in Boston will be ordered to close for general in-person use starting Wednesday as the city reintroduces COVID-19 restrictions as part of a larger, regional strategy that Mayor Martin Walsh said is meant to combat the post-Thanksgiving surge in coronavirus activity. The Boston Public Health Commission on Monday issued a supplemental order moving the city back to a modified version of Step 2, Phase 2 of the state's economic reopening strategy for at least three weeks beginning Wednesday. Walsh said the curtailment of allowable activity "is not about targeting specific sectors that cause the virus. This is an effort to reduce overall activity outside the home using mechanisms afforded by the state's reopening plan."