Remove tabs after spaces in C comments

This was not changed in HEAD, but will be done later as part of a
pgindent run.  Future pgindent runs will also do this.

Report by Tom Lane

Backpatch through all supported branches, but not HEAD

src/interfaces/ecpg/test/expected/thread-alloc.c

@@ -74,7 +74,7 @@ struct sqlca_t
 	/* Element 0: set to 'W' if at least one other is 'W'	*/
 	/* 1: if 'W' at least one character string		*/
 	/* value was truncated when it was			*/
-	/* stored into a host variable.				*/
+	/* stored into a host variable.             */
 
 	/*
 	 * 2: if 'W' a (hopefully) non-fatal notice occurred