chore: say which repository each source_ref cites

Profiles that read two repositories, a libretro port and its upstream,
now prefix each citation with source or upstream, decided by which tree
carries the cited value at its pin. The emulator pages use the word to
tell libretro glue, emulator code as the port carries it, and the
upstream emulator apart.

emulators/same_cdi.yml

@@ -46,7 +46,7 @@ files:
     system: cdi
     required: true
     note: "Forced system. Main CPU BIOS (3 region variants via MAME BIOS switch) + servo/slave MCU dumps. vmpega.rom is ROM_LOAD_OPTIONAL: full-motion video needs it, the machine starts without it."
-    source_ref: "src/mame/drivers/cdi.cpp:713"
+    source_ref: "source src/mame/drivers/cdi.cpp:713"
     contents:
       - name: cdi200.rom
         description: Magnavox CD-i 200 BIOS (default, US)
@@ -85,7 +85,7 @@ files:
     system: cdi
     required: false
     note: "CD-i Mono-II (NTSC). MACHINE_NOT_WORKING. Listed in .info as optional."
-    source_ref: "src/mame/drivers/cdi.cpp:714"
+    source_ref: "source src/mame/drivers/cdi.cpp:714"
     contents:
       - name: "philips__cdi-220_ph3_r1.2__mb834200b-15__02f_aa__9402_z04.tc574200-le._1.7211"
         description: Mono-II main CPU BIOS, Philips CDI-220 PH3 R1.2
@@ -109,7 +109,7 @@ files:
     system: cdi
     required: false
     note: "CD-i 910-17P Mini-MMC (PAL). MACHINE_NOT_WORKING. Not in .info firmware list."
-    source_ref: "src/mame/drivers/cdi.cpp:715"
+    source_ref: "source src/mame/drivers/cdi.cpp:715"
     contents:
       - name: "philips__cd-i_2.1__mb834200b-15__26b_aa__9224_z01.tc574200.7211"
         description: CD-i 910-17P Mini-MMC BIOS (default)
@@ -148,7 +148,7 @@ files:
     system: cdi
     required: false
     note: "CD-i 490. MACHINE_NOT_WORKING. Not in .info firmware list."
-    source_ref: "src/mame/drivers/cdi.cpp:716"
+    source_ref: "source src/mame/drivers/cdi.cpp:716"
     contents:
       - name: cdi490a.rom
         description: CD-i 490 main CPU BIOS