apibuild: Simplify strip_lead_star()

The method strip_lead_star() removes a single leading asterisk
character from a string by ignoring leading whitespace, otherwise it
returns the original string.

This could be achieved with a single if-statement followed by replace.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Radostin Stoyanov <rstoyanov1@gmail.com>

docs/apibuild.py

@@ -721,15 +721,8 @@ class CParser:
         self.index.info = res
 
     def strip_lead_star(self, line):
-        l = len(line)
+        if line.lstrip().startswith('*'):
-        i = 0
+            line = line.replace('*', '', 1)
-        while i < l:
-            if line[i] == ' ' or line[i] == '\t':
-                i += 1
-            elif line[i] == '*':
-                return line[:i] + line[i + 1:]
-            else:
-                return line
         return line
 
     def cleanupComment(self):