Remove unnecessary test for xc == 1 in _pydecimal (GH-27102)

- if `xc == 1` then the function returns on line 2140;
- other assignments to `xc` are inside the `y.sign == 1` condition block which always returns early

Author: donno2048

Lib/_pydecimal.py

@@ -2230,7 +2230,7 @@ def _power_exact(self, other, p):
             if xe != 0 and len(str(abs(yc*xe))) <= -ye:
                 return None
             xc_bits = _nbits(xc)
-            if xc != 1 and len(str(abs(yc)*xc_bits)) <= -ye:
+            if len(str(abs(yc)*xc_bits)) <= -ye:
                 return None
             m, n = yc, 10**(-ye)
             while m % 2 == n % 2 == 0:
@@ -2243,7 +2243,7 @@ def _power_exact(self, other, p):
         # compute nth root of xc*10**xe
         if n > 1:
             # if 1 < xc < 2**n then xc isn't an nth power
-            if xc != 1 and xc_bits <= n:
+            if xc_bits <= n:
                 return None
 
             xe, rem = divmod(xe, n)