chore: remove repetitive words

Signed-off-by: CoolCu <coolcui@qq.com>

languages/C.txt

@@ -145,7 +145,7 @@ Operators
   %= 	  modulo and store
   <<=  	shift left and store
   >>=  	shift right and store
-  &=   	bitwise and and store
+  &=   	bitwise and store
   ^=   	bitwise exclusive or and store
   |=   	bitwise or and store
   ,    	separator as in   ( y=x,z=++x )

languages/python.md

@@ -120,7 +120,7 @@
 |  %= | modulo and store|
 | <<= | shift left and store|
 |  \>>= | shift right and store|
-|  &= | bitwise and and store|
+|  &= | bitwise and store|
 |  ^= | bitwise exclusive or and store|
 |  \|= | bitwise or and store|
 |  , | separator as in   ( y=x,z=++x )|