Revert "nano: bump to version 2.7.5"

The bump causes build failure with musl, this new version uses with
undefined REG_STARTEND which is a glibc-ism that isn't available for
musl-based toolchains.
The introduction of this is to address
https://savannah.gnu.org/bugs/?50030 so it's not quite straightforward
to fix.

This reverts commit d0035543432edddee4dcb017ac4dd74832133e89.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/nano/nano.hash

@@ -1,2 +1,2 @@
 # Locally calculated after checking pgp signature
-sha256 a64d24e6bc4fc448376d038f9a755af77f8e748c9051b6f45bf85e783a7e67e4  nano-2.7.5.tar.xz
+sha256 752170643039e2c95a433de357f0c70a8c4c4c561a90a7e7259a63e225b659b9  nano-2.7.4.tar.xz

package/nano/nano.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 NANO_VERSION_MAJOR = 2.7
-NANO_VERSION = $(NANO_VERSION_MAJOR).5
+NANO_VERSION = $(NANO_VERSION_MAJOR).4
 NANO_SITE = https://www.nano-editor.org/dist/v$(NANO_VERSION_MAJOR)
 NANO_SOURCE = nano-$(NANO_VERSION).tar.xz
 NANO_LICENSE = GPLv3+