WASHINGTON—The Federal Reserve said Wednesday that the economy was growing at a modest pace at the end of 2021 but was still being held back by ongoing supply-chain disruptions and labor shortages. In its latest survey of business conditions around the country, the Fed said its 12 regional banks found that the economy was continuing to grow. But many regions reported a sudden pullback in spending on leisure travel, hotels, and restaurants because of the spread of the Omicron variant of the coronavirus. “Although optimism remained high generally, several districts cited reports from businesses that expectations for growth over the next several months cooled somewhat during the last few weeks” of 2021, a period when COVID-19 cases were rising sharply. Of the Fed’s 12 districts, only one, Dallas, reported “robust” growth in the closing weeks of 2021. But even in that district, Fed officials noted that “uncertainty increased amid a …