Существует несколько решений:
JavascriptExecutor js = (JavascriptExecutor) driver;
WebElement element = driver.findElement(By.cssSelector(".maps-header-text-h1 #currentMapCategory"));
String headerText = (String) js.executeScript("return arguments[0].previousSibling.textContent", element).trim();
Второе:
String headerText = driver.findElement(By.cssSelector(".maps-header-text-h1")).getText();
String mapCategoryText = driver.findElement(By.cssSelector("#currentMapCategory")).getText();
String headerText = headerText.replace(mapCategoryText, "").trim();
Третье:
JavascriptExecutor js = (JavascriptExecutor) driver;
WebElement element = driver.findElement(By.cssSelector(".maps-header-text-h1"));
String headerText = (String) js.executeScript("return arguments[0].firstChild.textContent", element).trim();
Еще одно от @KunduK:
// split("\\s") means split by whitespace, that can be space, tab, newline..
String headerText = driver.findElement(By.cssSelector(".maps-header-text-h1"))
.getText().trim()
.split("\\s")[0];